Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Denominator (all weighted averages) Weighted Average Number of Shares Outstanding, Diluted [Abstract] Non-investment grade Internal Noninvestment Grade [Member] Trading Arrangement: Trading Arrangement [Axis] 15020 and 15030 Conference Center Drive 15020 and 15030 Conference Center Drive [Member] 15020 and 15030 Conference Center Drive Maximum Maximum [Member] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Statistical Measurement [Domain] Statistical Measurement [Domain] Conversion of common units Exchangeable Common Units [Member] Incremental weighted average common shares attributable to common units in the operating partnership that may be exchanged for common shares. Title of 12(b) Security Title of 12(b) Security Numerator for diluted EPS on net income attributable to common shareholders Net Income (Loss) Available to Common Stockholders, Diluted Carrying Amount Reported Value Measurement [Member] Document Fiscal Year Focus Document Fiscal Year Focus Revenue, allocated to remaining performance obligations, expected timing of satisfaction, period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period 4.50%, $400,000 aggregate principal Unsecured Senior Notes Due October 2030 [Member] Unsecured Senior Notes Due October 2030 Guaranteed maximum price Guaranteed Maximum Price [Member] Guaranteed Maximum Price [Member] Weighted average interest rate Debt, Weighted Average Interest Rate Adjustment to Compensation, Amount Adjustment to Compensation Amount Pledged Status [Axis] Pledged Status [Axis] Financial Instrument [Axis] Financial Instrument [Axis] Proceeds from debt Proceeds from Issuance of Long-Term Debt [Abstract] Number of Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Real Estate [Line Items] Real Estate [Line Items] Deferred rent receivable Deferred Rent Receivables, Net Segment Reporting [Abstract] Segment Reporting [Abstract] Common Shares of beneficial interest ($0.01 par value; 150,000,000 shares authorized; shares issued and outstanding of 113,411,882 at June 30, 2026 and 113,210,642 at December 31, 2025) Common Stock, Value, Issued 2027 Lessee, Operating Lease, Liability, to be Paid, Year One Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Award performance period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Requisite Service Period Leases Lessee, Finance Leases [Text Block] Maximum exposure Guarantor Obligations, Maximum Exposure, Undiscounted Line of Credit Line of Credit [Member] Restatement Determination Date Restatement Determination Date Real Estate Property Classification [Domain] Real Estate Property Classification [Domain] Represents classification of real estate properties. Investments in unconsolidated real estate joint ventures Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Beginning balance Ending balance Contract with Customer, Asset, after Allowance for Credit Loss 2027 Finance Lease, Liability, to be Paid, Year One Derivative Instrument Risk [Axis] Derivative Instrument [Axis] PIUs Profit Interest Units [Member] Profit Interest Units [Member] Income attributable to share-based compensation awards for basic EPS Participating Securities, Distributed and Undistributed Earnings (Loss), Basic Beginning balance Ending balance Accounts Receivable, Allowance for Credit Loss Construction Contract Revenue Construction Contract Revenue [Member] Construction Contract Revenue [Member] Investing Receivables Financing Receivables [Text Block] Contract with Customer, Basis of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Exchange price (in dollars per share) Debt Instrument, Convertible, Conversion Price Operating lease cost Operating Lease Cost [Abstract] Operating Lease Cost Amendment Flag Amendment Flag Consolidated Entities [Axis] Consolidated Entities [Axis] Net credit loss expense (recoveries) Accounts Receivable, Credit Loss Expense (Reversal) Earned performance-based awards payout granted on 75th or greater percentile rank Share-based Compensation Arrangement by Share-based Payment Award of Earned, Payout Percentage Based on Percentile Rank Greater than or Equals to 75 Represents the earned payout, as a percentage of units granted, if the entity's total shareholder return relative to a peer group of companies ranks at the 75th percentile or greater. Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Financing cash flows for finance leases Finance Lease, Principal Payments Less: Accumulated depreciation Real Estate Investment Property, Accumulated Depreciation Property operating expenses Property operating expenses Cost of Other Property Operating Expense Loss Contingencies [Table] Loss Contingencies [Table] Leases [Abstract] Leases [Abstract] Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax [Abstract] Consolidated Entities [Domain] Consolidated Entities [Domain] Quark JV LLC Quark JV LLC [Member] Quark JV LLC Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Entity Address, State or Province Entity Address, State or Province PEO Total Compensation Amount PEO Total Compensation Amount Common shares of beneficial interest, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Assets Assets, Fair Value Disclosure [Abstract] Additions to long-lived assets Segment Reporting, Long-Lived Asset, Expenditure for Addition Asset Acquisition [Axis] Asset Acquisition [Axis] Non-Operating Properties in Aberdeen, Maryland Non-Operating Properties in Aberdeen, Maryland [Member] Non-Operating Properties in Aberdeen, Maryland Unvested at the beginning of the period (in shares or units) Unvested at the end of the period (in shares or units) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Denominator for basic EPS (common shares) (in shares) Weighted Average Number of Shares Outstanding, Basic Notional Amount Derivative, Notional Amount Percent of award distribution rights Share-based Compensation Arrangement by Share-based Payment Award, Distribution Rights as a Percentage of Non-PIU Common Units, Percentage Share-based Compensation Arrangement by Share-based Payment Award, Distribution Rights as a Percentage of Non-PIU Common Units, Percentage Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Commitments and Contingencies Loss Contingencies [Line Items] Stevens Investors, LLC Stevens Investors, LLC [Member] Stevens Investors, LLC [Member] Number of reportable segments Number of Reportable Segments Greater Washington, DC/Baltimore Greater Washington, DC/Baltimore [Member] Greater Washington, DC/Baltimore Financing Receivable, Credit Quality Indicator [Line Items] Financing Receivable, Credit Quality Indicator [Line Items] 2030 Lessee, Operating Lease, Liability, to be Paid, Year Four Lease liabilities Lease Liabilities [Abstract] Lease Liabilities Schedule of Key Terms and Fair Values of Interest Rate Swap Derivatives Schedule of Derivative Instruments [Table Text Block] 2.00%, $400,000 aggregate principal Unsecured Senior Notes Due January 2029 [Member] Unsecured Senior Notes Due January 2029 Entity Address, City or Town Entity Address, City or Town Consolidated Statements of Cash Flows Consolidated Statement of Cash Flows [Policy Text Block] Consolidated Statement of Cash Flows Granted (in shares or units) Awards granted (in shares or units) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Finance lease cost Finance Lease Cost [Abstract] Finance Lease Cost Share-Based Compensation Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Land controlled for development Land Controlled For Development [Member] Represents land controlled by the entity for future development. Class of Financing Receivable [Domain] Class of Financing Receivable [Domain] Tenant Notes Receivable Tenant notes receivable Tenant Notes Receivables [Member] Tenant Notes Receivables [Member] Receivables [Abstract] Receivables [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Assets held for sale Disposal Group, Including Discontinued Operation, Assets Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Vested (in shares or units) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Earned performance-based awards payout granted on 50th percentile rank Share-based Compensation Arrangement by Share-based Payment Award of Earned, Payout Percentage Based on Percentile Rank Equals to 50 Represents the earned payout, as a percentage of units granted, if the entity's total shareholder return relative to a peer group of companies ranks at the 50th percentile. Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Earned award payout as a percentage of target award Share-Based Compensation Arrangement by Share-Based Payment Award, Actual Payout Percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Actual Payout Percentage Redemption of common units Partners' Capital Account, Redemptions Numerator for basic EPS on net income attributable to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Stock issued for settlement of vested awards, aggregate fair value Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period, Aggregate Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period, Aggregate Fair Value Receivable [Domain] Receivable [Domain] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Total other comprehensive loss Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Schedule of Reconciliation of Segment Assets to Total Assets Segment Reporting, Reconciliation of Asset by Segment to Consolidated [Table Text Block] Fair value of interest rate swaps Interest Rate Derivatives, at Fair Value, Net Change in net deferred rent receivable and liability Straight Line Rent Name of Property [Axis] Name of Property [Axis] Gross SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Gross Earned performance-based awards payout granted on percentile rank below 25th Share-based Compensation Arrangement by Share-based Payment Award of Earned, Payout Percentage Based on Percentile Rank Less than 25 Represents the earned payout percentage based on percentile rank below 25. Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Investments in Sales-Type Leases Investment in Sales-Type Leases [Member] Investment in Sales-Type Leases Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Land Land [Member] Schedule of Segment Financial Information for Reportable Segments Segment Reporting [Table Text Block] Noncontrolling Interests Noncontrolling Interest [Member] Noncontrolling interests in subsidiaries Equity, Attributable to Noncontrolling Interest [Abstract] Term Loan Facility Unsecured Debt [Member] Schedule of Reconciliation of UJV NOI Allocable to COPT Defense to Equity in Income of Unconsolidated Entities Schedule of Reconciliation of Unconsolidated Joint Venture Net Operating Income to Equity in Income of Unconsolidated Entities [Table Text Block] Schedule of Reconciliation of Unconsolidated Joint Venture Net Operating Income to Equity in Income of Unconsolidated Entities [Table Text Block] Redeemable Noncontrolling Interest Noncontrolling Interest Disclosure [Text Block] Interest rate derivatives Interest Rate Derivative Assets, at Fair Value PB PIU Grants 2023 PB PIU Grants 2023 [Member] PB PIU Grants 2023 Notional amount of interest rate derivatives after scheduled amortization Interest Rate Cash Flow Hedge, Derivative Notional Amount after Scheduled Amortization Represents the notional amount of interest rate derivatives after scheduled amortization. Rents received in advance and security deposits Advance Rent and Security Deposit Liability Amount at the balance sheet date that has been received by the entity that represents collections of cash or other assets related to real estate operations revenue for which revenue has not yet been recognized and money paid in advance to protect the provider of a product or service, such as a lessor, against damage or nonpayment by the buyer or tenant (lessee) during the term of the agreement. Such damages may include physical damage to the property, theft of property, and other contractual breaches. Security deposits held may be interest or noninterest bearing. Debt, net Total debt, net Long-Term Debt Interest rate swap, effective August 1, 2019 Interest Rate Swap, Effective August 1, 2019 [Member] Interest Rate Swap, Effective August 1, 2019 [Member] Schedule of Payments Due on Property Operating Leases Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Supplemental schedule of non-cash investing and financing activities Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Document Period End Date Document Period End Date Changes in operating assets and liabilities Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Aggregate principal Debt Instrument, Face Amount Gain on sales of real estate Gain on sales of real estate Gain (Loss) on Sale of Properties 2028 Lessee, Operating Lease, Liability, to be Paid, Year Two Equity Equity [Text Block] Earnings per common share Earnings Per Share, Basic [Abstract] Security Exchange Name Security Exchange Name Schedule of Reconciliation of Segment Revenues to Total Revenues Segment Reporting, Reconciliation of Revenue by Segment to Consolidated [Table Text Block] Effective interest rate Debt Instrument, Interest Rate, Effective Percentage Leases Lessor, Operating Leases [Text Block] Weighted average restricted shares and deferred shares Restricted Stock and Deferred Shares [Member] Restricted Stock and Deferred Shares [Member] Amortized cost basis Total Financing Receivable, before Allowance for Credit Loss Finance leases, weighted average remaining lease term Finance Lease, Weighted Average Remaining Lease Term Aggregate fair value of awards vested Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Cash and cash equivalents and restricted cash Cash and Cash Equivalent [Abstract] Finance leases - Property Finance Lease, Right-of-Use Asset, after Accumulated Amortization Schedule of Operating Properties, Net Property, Plant, and Equipment [Table Text Block] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Earnings Per Share (“EPS”) Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Basic earnings per common share: Earnings Per Share [Abstract] Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Investing Receivables Investing receivables Investing Receivables [Member] Investing Receivables [Member] Document Fiscal Period Focus Document Fiscal Period Focus Lease Revenue Lease Income Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Other Assets Other Asset [Member] Other Asset Total liabilities Total Liabilities Liabilities Trading Symbol Trading Symbol Geographical [Domain] Geographical [Domain] Schedule of Interest Expense Interest Income and Interest Expense Disclosure [Table Text Block] Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Financing Receivable, Allowance for Credit Loss [Line Items] Financing Receivable, Allowance for Credit Loss [Line Items] 2.25%, $400,000 aggregate principal Unsecured Senior Notes Due March 2026 [Member] Unsecured Senior Notes Due March 2026 Purchase price Asset Acquisition, Consideration Transferred, Excluding Transaction Costs Asset Acquisition, Consideration Transferred, Excluding Transaction Costs Company Selected Measure Name Company Selected Measure Name Amortization of deferred financing costs and net debt discounts Amortization of Debt Issuance Costs and Discounts Fixed Rate Derivative, Fixed Interest Rate Minimum payout percentage if TSR percentile rank exceeds the 50th percentile and TSR is negative Share-Based Compensation Arrangement by Share-Based Payment Award, Minimum Payout Percentage When Total Shareholder Return (TSR) Percentile Rank Exceeds 50th Percentile and TSR Is Negative Share-Based Compensation Arrangement by Share-Based Payment Award, Minimum Payout Percentage When Total Shareholder Return (TSR) Percentile Rank Exceeds 50th Percentile and TSR Is Negative Adjustment to income attributable to share-based compensation awards for diluted EPS Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units Navy Support Navy Support [Member] Navy Support Long-term debt, gross Total Long-Term Debt, Gross Credit Facility [Domain] Credit Facility [Domain] Depreciation and amortization associated with real estate operations Depreciation and other amortization associated with real estate operations Depreciation, Depletion and Amortization, Nonproduction Reconciliation of net income to net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Compensation Amount Outstanding Recovery Compensation Amount Individual: Individual [Axis] Denominator for diluted EPS (common shares) (in shares) Weighted Average Number of Shares Outstanding, Diluted Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Entity Emerging Growth Company Entity Emerging Growth Company Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Leasing costs paid Payment for Initial Direct Cost, Lease, Investing Activity 2028 Finance Lease, Liability, to be Paid, Year Two Disposal Group Name [Domain] Disposal Group Name [Domain] 2026 Financing Receivable, Year One, Originated, Current Fiscal Year Credit Loss [Abstract] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Thereafter Finance Lease, Liability, Payments Due After Year Four Finance Lease, Liability, Payments Due After Year Four Dividends Dividends 2030 Finance Lease, Liability, to be Paid, Year Four Interest Rate Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block] Decrease in accrued capital improvements, leasing, and other investing activity costs Increase (Decrease) in Accrued Capital Improvements Leasing and Other Investing Activity Costs The net change during the reporting period in future cash outflow to pay for purchases of fixed assets, construction in progress expenditures, deferred leasing costs and other investing activity costs that have occurred. Dividends and distributions payable Dividends/distributions payable Dividends Payable Notes receivable from the City of Huntsville Notes Receivable from City of Huntsville [Member] Represents notes receivable from City of Huntsville. Less: Amount representing interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Less: Income from UJV allocable to COPT Defense attributable to depreciation and amortization expense, interest expense, gain on sale of real estate, and loss on early extinguishment of debt Income (Loss) from Equity Method Investments Allocable to Depreciation, Amortization, Interest Expense And Gain (Loss) On Debt Extinguishment Income (Loss) from Equity Method Investments Allocable to Depreciation, Amortization, Interest Expense And Gain (Loss) On Debt Extinguishment Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Less: Amount representing interest Finance Lease, Liability, Undiscounted Excess Amount Operating cash flows for operating leases Operating Lease, Payments Award Timing Predetermined Award Timing Predetermined [Flag] Other capital improvements on operating properties Payments for Capital Improvements Cumulative distributions in excess of net income Accumulated Distributions in Excess of Net Income Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] 2024 Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year Variable-lease revenue Variable Lease, Income Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Exchange rate of notes Debt Instrument, Convertible, Conversion Ratio Total lease payments Lessee, Operating Lease, Liability, to be Paid Area of real estate property (in sqft or acres) Area of real estate property (in acres) Area of Real Estate Property Change in Contract with Customer, Asset Change in Contract with Customer, Asset [Abstract] Lessor, Lease, Description [Table] Lessor, Lease, Description [Table] Real Estate Joint Ventures Real Estate Joint Ventures Disclosure [Text Block] This block of text may be used to disclose details concerning consolidated and unconsolidated real estate joint ventures. Dilutive effect of share-based compensation awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Share-based compensation Shares Granted, Value, Share-Based Payment Arrangement, after Forfeiture 5.25%, $345,000 aggregate principal Unsecured Senior Notes Due September 2028 [Member] Unsecured Senior Notes Due September 2028 Unvested at the beginning of the period (in dollars per share or unit) Unvested at the end of the period (in dollars per share or unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value All Executive Categories All Executive Categories [Member] Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Revolving Credit Facility Repayments of Long-Term Lines of Credit Long-term debt Long-Term Debt, Fair Value Extension fee percentage Debt Instrument, Extension Fee Percentage Debt Instrument, Extension Fee Percentage Redeemable noncontrolling interest Redeemable Noncontrolling Interest, Equity, Carrying Amount Plan Name [Domain] Plan Name [Domain] Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities [Axis] Asset Acquisition [Domain] Asset Acquisition [Domain] Performance-based PIU's Performance-Based Profit Interest Units [Member] Performance-Based Profit Interest Units [Member] Property - operating lease right-of-use assets Operating leases - Property Operating Lease, Right-of-Use Asset Interest rate Note Receivable, Terms, Interest Rate Note Receivable, Terms, Interest Rate Approximate gains to be reclassified from AOCL to interest expense over the next 12 months Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Schedule of Calculation of Numerator and Denominator in Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Information by Business Segment Segment Reporting [Text Block] Minimum Minimum [Member] Maximum environmental indemnification to the tenant against consequential damages after acquisition of property Maximum Additional Costs Agreed To Be Paid By The Entity Under Environmental Indemnification Agreement Maximum additional costs agreed to be paid by the entity under environmental indemnification agreement Common share dividends paid Payments of Ordinary Dividends, Common Stock Expiration Date Trading Arrangement Expiration Date 2030 Long-Term Debt, Maturity, Year Four Real Estate [Table] Real Estate [Table] Schedule of Construction Contract and Other Service Revenues by Compensation Arrangement Disaggregation of Revenue [Table Text Block] Liabilities Liabilities [Abstract] Income Statement Location [Axis] Location, Statement of Income, Balance [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Limited partners' capital account, units outstanding (in units) Limited Partners' Capital Account, Units Outstanding Total equity Balance Balance Equity, Including Portion Attributable to Noncontrolling Interest Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Investment grade Internal Investment Grade [Member] Accrued interest receivable, net of allowance for credit losses Financing Receivable, Accrued Interest, after Allowance for Credit Loss Other liabilities Other Liabilities Estimate of possible loss (up to) Loss Contingency, Estimate of Possible Loss Buildings and improvements Building and Building Improvements [Member] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Derivative [Table] Derivative [Table] Financing Receivable, Allowance for Credit Loss [Table] Financing Receivable, Allowance for Credit Loss [Table] Common shares of beneficial interest, shares authorized (in shares) Common Stock, Shares Authorized Total properties, net Real Estate Investment Property, Net Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Schedule of Fair Value of Debt Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Exercise Price Award Exercise Price Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Segment financial information for real estate operations Segment Reporting [Line Items] Document Quarterly Report Document Quarterly Report Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Segments [Domain] Segments [Domain] Revolving Development Facility Revolving Development Facility [Member] Revolving Development Facility Interest rate swaps Interest Rate Swap [Member] Operating Properties Operating Properties [Member] Represents information pertaining to operating properties of the entity. Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss At the market offering program, aggregate gross sales price At Market Stock, Offering Program Established, Aggregate Value Aggregate gross sales price of common shares that may be issued in an at-the-market stock offering program established by the Company. Investment in sales-type lease Sales-type Lease, Net Investment in Lease, Purchase Income before equity in income of unconsolidated entities and income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Time-based PIU's Time-Based Profit Interest Units [Member] Time-based Profit Interest Units [Member] Debt, Net Debt Disclosure [Text Block] Investing receivables (net of allowance for credit losses of $2,238 and $3,575, respectively) Investing receivables, net Financing Receivable, after Allowance for Credit Loss Net discounts and deferred financing costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Net deferred financing costs Debt Issuance Costs, Net Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Carrying Value of Investment Carrying values of investments in UJVs owning operating properties, net of deficit investment balances Investments in UJVs deficit balances included in segment assets Equity Method Investments Properties, Net Real Estate Disclosure [Text Block] Equity Component [Domain] Equity Component [Domain] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Mortgage and Other Secured Debt Secured Debt [Member] Total operating expenses Costs and Expenses Adoption Date Trading Arrangement Adoption Date Finance leases, weighted average discount rate Finance Lease, Weighted Average Discount Rate, Percent Sale of non-operating properties, consideration Disposal Group, Including Discontinued Operation, Consideration Counterparty Name [Domain] Counterparty Name [Domain] Interest rate Debt Instrument, Interest Rate, Stated Percentage Total shareholders’ equity Equity, Attributable to Parent 2.90%, $400,000 aggregate principal Unsecured Senior Notes Due December 2033 [Member] Unsecured Senior Notes Due December 2033 Other consolidated entities Minority Interest in Net Income (Loss) Other Including Joint Ventures Minority Interests Amount of net income (loss) for the period allocated to noncontrolling shareholders, partners, or other equity holders in one or more of the entities consolidated into the reporting entity's financial statements other than operating partnerships or interests held by preferred unit holders. Payout percentage reduction when TSR percentile rank exceeds target and TSR is negative Share-Based Compensation Arrangement by Share-Based Payment Award, Payout Percentage Reduction When Total Shareholders Return (TSR) Percentile Rank Exceeds Target and TSR Is Negative Share-Based Compensation Arrangement by Share-Based Payment Award, Payout Percentage Reduction When Total Shareholders Return (TSR) Percentile Rank Exceeds Target and TSR Is Negative Assets Assets [Abstract] Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Accounting Policies [Abstract] Accounting Policies [Abstract] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Risk-free interest rate Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Schedule of Credit Risk Classification Financing Receivable Credit Quality Indicators [Table Text Block] Other fixed-rate debt Other Fixed Rate Debt [Member] Fixed-rate debt excluding other fixed rate debt not separately disclosed. Property - operating lease liabilities Operating leases - Property Lease liability Operating Lease, Liability Insider Trading Policies and Procedures [Line Items] Finance leases - Property Lease liability Finance Lease, Liability Other Other Services Revenue [Member] Other Services Revenue [Member] Schedule of Restricted Share and TB-PIU Activity Schedule of Nonvested Share Activity [Table Text Block] Other Proceeds from (Payment for) Other Financing Activity Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Interest rate swaps designated as cash flow hedges Interest Rate Cash Flow Hedge Asset at Fair Value General, administrative, leasing, and other expenses General, administrative, leasing, and other expenses Selling, General and Administrative Expense Preferred distributions of annual operating cash flows to partner Preferred Distributions of Annual Operating Cash Flows to Partner Preferred Distributions of Annual Operating Cash Flows to Partner Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Lease revenue Operating Lease, Lease Income Weighted average antidilutive securities excluded from computation of diluted earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Schedule of Securities Excluded from Computation of Diluted Earnings Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Entity Central Index Key Entity Central Index Key Real Estate Properties Status [Axis] Real Estate Properties Status [Axis] Information by status of the property. Schedule of Payouts for Performance-Based Awards Schedule of Share-based Compensation Arrangement by Share-based Payment Award For Performance Shares [Table Text Block] Schedule of Share-based Compensation Arrangement by Share-based Payment Award For Performance Shares Extension option period Debt Instrument, Extension Option, Term Represents the period over which the debt may be extended at the option of the entity, subject to certain conditions. Award Level [Axis] Award Level [Axis] Award Level All Adjustments to Compensation All Adjustments to Compensation [Member] Service operations Other assets Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Name of Property [Domain] Name of Property [Domain] Equity [Abstract] Equity [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Beginning balance Ending balance Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss 2026 Long-Term Debt, Maturity, Remainder of Fiscal Year Investing receivables funded Payments to Acquire Notes Receivable Income Statement [Abstract] Income Statement [Abstract] Shareholders’ equity Equity, Attributable to Parent [Abstract] Document Transition Report Document Transition Report Ownership [Axis] Ownership [Axis] Decrease in accounts payable, accrued expenses, and other liabilities Increase (Decrease) in Operating Liabilities Target Level Target Level [Member] Target Level Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Investment, Name [Axis] Investment, Name [Axis] Finance leases, lease liability, location Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration] Designated Designated as Hedging Instrument [Member] Finance leases - right-of-use assets, location Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] Schedule of Computation of NOI from Service Operations Schedule of Net Operating Income from Segments from Service Operations [Table Text Block] Tabular disclosure of the computation of net operating income from service operations. Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Unsecured note payable Unsecured Note Payable Due May 2026 [Member] Unsecured Note Payable Due May 2026 Repayments of debt Repayments of Long-Term Debt [Abstract] Variable rate, spread over SOFR Debt Instrument, Basis Spread on Variable Rate Lessor, Lease, Description [Line Items] Lessor, Lease, Description [Line Items] Other Commitments [Domain] Other Commitments [Domain] City Area Code City Area Code Restricted shares Restricted Stock [Member] Total lease payments Finance Lease, Liability, to be Paid Acquisition of investment in sales-type lease Payment for Acquisition, Lease, Held-for-Investment Conversion of common units to common shares Stock Issued During Period, Value, Conversion of Units Accumulated Other Comprehensive Income AOCI Attributable to Parent [Member] B RE COPT DC JV II LLC B RE COPT DC JV II LLC [Member] B RE COPT DC JV II LLC Decrease in fair value of derivatives applied to accumulated other comprehensive income/loss and noncontrolling interests Increase (Decrease) in Fair Value of Derivatives Applied to Aocl and Noncontrolling Interests Increase in fair value of derivatives applied to Accumulated Other Comprehensive (Loss) Profit and noncontrolling interests All Individuals All Individuals [Member] Variable rate, additional spread over SOFR Debt Instrument, Additional Basis Spread on Variable Rate Debt Instrument, Additional Basis Spread on Variable Rate Name Forgone Recovery, Individual Name Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Weighted Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Statement [Line Items] Statement [Line Items] Total assets Total Assets Segment assets Total consolidated assets Assets Property Operating Leases Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract] Entity [Domain] Entity [Domain] Conversion of redeemable noncontrolling interest Redeemable Noncontrolling Interest [Member] Redeemable Noncontrolling Interest [Member] Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] The number of percentile ranks to fall between to earn interpolated PB-PIUs between such percentile ranks, conditioned on the percentile rank exceeding 25% Number of Percentile Ranks to Fall Between to Earn Interpolated PSU The number of percentile ranks to fall between to earn interpolated PSUs between such percentile ranks, conditioned on the percentile rank exceeding 25%. Financing Receivable, Credit Quality Indicator [Table] Financing Receivable, Credit Quality Indicator [Table] Reportable segments Operating Segments [Member] Interest expense Interest expense Interest Expense, Nonoperating COPT Defense Properties, L.P. COPT Defense Properties, LP [Member] COPT Defense Properties, LP Carrying value of lessee right-of-use asset Total right-of-use assets Lease, Right-of-Use Assets Lease, Right-of-Use Assets Share-Based Compensation Share-Based Payment Arrangement [Text Block] Organization Nature of Operations [Text Block] PEO PEO [Member] 2028 Long-Term Debt, Maturity, Year Two Credit Losses on Financial Assets and Other Instruments Credit Loss, Financial Instrument [Text Block] Minimum payout percentage if TSR is at least 6% Share-Based Compensation Arrangement by Share-Based Payment Award, Minimum Payout Percentage If Total Shareholder Return Is At Least Six Percent Share-Based Compensation Arrangement by Share-Based Payment Award, Minimum Payout Percentage If Total Shareholder Return Is At Least Six Percent Measurement Basis [Axis] Measurement Basis [Axis] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Granted (in dollars per share or unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Credit Losses, Financial Assets and Other Instruments [Roll Forward] Credit Losses, Financial Assets and Other Instruments [Roll Forward] Credit Losses, Financial Assets and Other Instruments Portion of beginning balance recognized in revenue Contract with Customer, Liability, Revenue Recognized 2022 Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year Revolving Credit Facility Revolving Credit Facility [Member] Forfeited (in dollars per share or unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value 2023 Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Increase (Decrease) in Shareholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Common shares of beneficial interest, shares outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Award Timing Disclosures [Line Items] Net income attributable to common shareholders - diluted (in dollars per share) Diluted EPS attributable to common shareholders (in dollars per share) Earnings Per Share, Diluted Entity Current Reporting Status Entity Current Reporting Status Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Total Shareholder Return Amount Total Shareholder Return Amount Net credit loss expense (recoveries) Financing Receivable, Credit Loss, Expense (Reversal) Interest costs capitalized Interest Costs Capitalized Unconsolidated real estate joint ventures owning operating properties Unconsolidated Real Estate Joint Ventures Owning Operating Properties [Member] Unconsolidated Real Estate Joint Ventures Owning Operating Properties 2021 and Earlier Financing Receivable, Originated, More than Five Years before Current Fiscal Year Percentage ownership in operating partnership Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest Ownership [Domain] Ownership [Domain] Schedule of Information Related to Investments in Consolidated Real Estate Joint Ventures Consolidated Real Estate, Joint Ventures [Table Text Block] Tabular disclosure of information pertaining to investments in consolidated real estate joint ventures. Revolving Credit Facility Proceeds from Long-Term Lines of Credit Adjustments to reconcile net income to net cash provided by operating activities Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Minimum payout percentage if TSR is at least 10% Share-Based Compensation Arrangement by Share-Based Payment Award, Minimum Payout Percentage If Total Shareholder Return Is At Least Ten Percent Share-Based Compensation Arrangement by Share-Based Payment Award, Minimum Payout Percentage If Total Shareholder Return Is At Least Ten Percent 2029 Long-Term Debt, Maturity, Year Three Difference between the joint venture's lower cost basis and the entity's share of underlying equity in the net assets Equity Method Investment, Difference Between Carrying Amount and Underlying Equity Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Construction contract and other service revenues Construction contract and other service revenues Revenue from Contract with Customer, Excluding Assessed Tax Transfers from non-operating properties Segment Reporting Transfers From (To) Non Operating Properties Represents amounts transferred from non operating properties to reported segments during the period resulting from properties being placed into service. Schedule of Composition of Sales-Type Lease Revenue Sales-type Lease, Lease Income [Table Text Block] Other debt repayments Repayments of Other Long-Term Debt Financial Instruments [Domain] Financial Instruments [Domain] Schedule of Information Related to Investments in Unconsolidated Real Estate Joint Ventures Equity Method Investments [Table Text Block] Investing receivable allowance for credit loss Allowance for credit losses Beginning balance Ending balance Financing Receivable, Allowance for Credit Loss Leases Lessor, Sales-type Leases [Text Block] Redemption of vested equity awards Stock Repurchased During Period, Value Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Underlying Securities Award Underlying Securities Amount Comprehensive income attributable to noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Estimated Fair Value Estimate of Fair Value Measurement [Member] Construction Contract and Other Service Revenues Revenue from Contract with Customer [Text Block] Subsegments [Domain] Subsegments [Domain] Other consolidated entities Other Noncontrolling Interests Redshift JV LLC Redshift JV LLC [Member] Redshift JV LLC Number of lease properties which were provided environmental indemnifications Property Subject to Environmental Indemnity, Number of Properties Represents the number of properties in New Jersey which were provided environmental indemnifications by the entity. Subsegments [Axis] Subsegments [Axis] Preferred Units Preferred Stock [Member] Other Payment for (Proceeds from) Other Investing Activity Operating leases, weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Right-of-use assets Lease Right of Use Assets [Abstract] Lease Right of Use Assets Schedule of Real Estate [Table] Schedule of Real Estate [Table] Schedule that includes carrying amount of properties, accumulated depreciation and other information for real estate properties, by status. Segment Reporting [Table] Segment Reporting [Table] Cumulative Distributions in Excess of Net Income Accumulated Distributions in Excess of Net Income [Member] Schedule of Debt Maturities Schedule of Maturities of Long-Term Debt [Table Text Block] Beginning balance Ending balance Contract with Customer, Receivable, after Allowance for Credit Loss Schedule of Equity Method Investments [Table] Equity Method Investment [Table] Schedule of Property Lease Costs and Effect of Property Lease Payments on Consolidated Statements of Cash Flows Lease, Cost [Table Text Block] Performance-Based Awards Performance Based Awards [Member] Performance Based Awards Lackland Air Force Base Lackland Air Force Base [Member] Lackland Air Force Base [Member] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] All Trading Arrangements All Trading Arrangements [Member] Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] NOI NOI Operating Income (Loss) Revenue, allocated to remaining performance obligations Revenue, Remaining Performance Obligation, Amount Other property revenue Other Property Revenue Other Property Revenue Current Fiscal Year End Date Current Fiscal Year End Date Schedule of Payments Due on Property Finance Leases Finance Lease, Liability, to be Paid, Maturity [Table Text Block] 2026 Finance Lease, Liability, to be Paid, Remainder of Fiscal Year Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Fair values of interest rate swap derivatives Derivative [Line Items] Total lease liabilities Operating properties lease liabilities included in segment assets Lease, Liability Lease, Liability Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Dividends declared per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Entity File Number Entity File Number Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Distributions to noncontrolling interest Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Antidilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Common shares of beneficial interest, shares issued (in shares) Common Stock, Shares, Issued Measure: Measure [Axis] Common units in COPT Defense Properties, L.P. (“CDPLP”) Noncontrolling Interest in Operating Partnerships Interest expense associated with amortization of debt discount and issuance costs Amortization of Debt Discount (Premium) Cash paid for amounts included in the measurement of lease liabilities Cash Flow, Operating Activities, Lessee [Abstract] Projects in development or held for future development Development in Process B RE COPT DC JV III LLC B RE COPT DC JV III LLC [Member] B RE COPT DC JV III LLC Contract with Customer, Basis of Pricing [Axis] Contract with Customer, Basis of Pricing [Axis] Real Estate Properties Status [Domain] Real Estate Properties Status [Domain] Represents the status of the property. Equity Components [Axis] Equity Components [Axis] PSUs Performance Share Units [Member] Performance Share Units Decrease (increase) in accounts receivable Increase (Decrease) in Accounts Receivable Product and Service [Domain] Product and Service [Domain] Tenant improvements on operating properties Payment for Leasehold Improvement, Lessor, Investing Activity Deferred incremental costs Capitalized Contract Cost, Net Net income attributable to common shareholders Net income attributable to common shareholders Net Income Loss Available To Common Stockholders, Including Participating Securities Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock; of income (loss) available to common shareholders, including participating securities. Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Distributions to owners of common units in CDPLP Minority Interest (Decrease) from Distributions to Operating Partnership Noncontrolling Interest Holders Decrease in noncontrolling interest balance from payment of distributions to noncontrolling interest holders in the Operating Partnership. Entity Interactive Data Current Entity Interactive Data Current Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Tax Incremental Financing Bond Tax Incremental Financing Bond [Member] Tax Incremental Financing Bond [Member] Net credit loss expense (recoveries) Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss, Expense (Reversal) Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss, Expense (Reversal) Decrease in redeemable noncontrolling interest and increase in equity to adjust for changes in fair value of redeemable noncontrolling interest Adjustments for changes in fair value of interest Noncontrolling Interest, Change in Redemption Value Conversion of common units to common shares (in shares) Stock Issued During Period, Shares, Conversion of Units Entity Small Business Entity Small Business Comprehensive income attributable to common shareholders Comprehensive Income (Loss), Net of Tax, Attributable to Parent Other segment items Segment Reporting, Other Segment Item [Abstract] Segment Reporting, Other Segment Item Net unamortized discounts and commissions Debt Instrument, Unamortized Discount 2029 Lessee, Operating Lease, Liability, to be Paid, Year Three Termination Date Trading Arrangement Termination Date Other Commitments [Axis] Other Commitments [Axis] Award Level [Domain] Award Level [Domain] Award Level [Domain] Fair Value, Recurring [Table] Fair Value, Recurring and Nonrecurring [Table] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Accumulated amortization of deferred leasing costs Deferred Initial Direct Cost, Lease, Accumulated Amortization 2029 Finance Lease, Liability, to be Paid, Year Three Document Type Document Type Assets and liabilities measured at fair value on a recurring basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Firm fixed price Fixed-Price Contract [Member] Fair Value as of Grant Date Award Grant Date Fair Value Aggregate grant date fair value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Aggregate Fair Value The aggregate fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reconciliation of cash and cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation [Abstract] Decrease in lease incentives, investments in sales-type leases, and prepaid expenses and other assets, net Increase (Decrease) in Lease Incentives, Investments in Sales-type Leases and Prepaid Expenses and Other Assets, Net Increase (Decrease) in Lease Incentives, Investments in Sales-type Leases and Prepaid Expenses and Other Assets, Net Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Decrease in noncontrolling interests and increase in shareholders’ equity in connection with the conversion of common units into common shares Equity Change Stock Issued During Period Value Conversion of Units Change in equity from stock issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real investment trust unit (UPREIT unit). Arrangement Duration Trading Arrangement Duration Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] NoVA Defense/IT NoVA Defense/IT [Member] NoVA Defense/IT Local Phone Number Local Phone Number Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Thereafter Long-Term Debt, Maturity, after Year Four Long-Term Debt, Maturity, after Year Four Pledged Status [Domain] Pledged Status [Domain] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Commitments and contingencies (Note 17) Commitments and Contingencies Total revenues Revenues from real estate operations Total revenues Revenues Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Equity in income of unconsolidated entities Equity in income of unconsolidated entities Equity in income of unconsolidated entities Income (Loss) from Equity Method Investments Redeemable Noncontrolling Interest [Roll Forward] Equity, Attributable to Noncontrolling Interest [Roll Forward] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Executive Category: Executive Category [Axis] Amortization of property right-of-use assets Finance Lease, Right-of-Use Asset, Amortization Receivable Type [Axis] Receivable Type [Axis] Deferred share awards Deferred Share Awards [Member] Deferred Share Awards [Member] Real Estate Property Classification [Axis] Real Estate Property Classification [Axis] Represents information regarding classification of real estate properties. Award vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Counterparty Name [Axis] Counterparty Name [Axis] Operating expenses Operating Costs and Expenses [Abstract] Liabilities and equity Liabilities and Equity [Abstract] Interest rate swap, effective February 1, 2023 3.747% Interest Rate Swap, Effective February 2023 3.747% [Member] Interest Rate Swap, Effective February 2023 3.747% Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Award Type [Domain] Award Type [Domain] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Interest on lease liabilities Finance Lease, Interest Expense 2026 Lessee, Operating Lease, Liability, to be Paid, Remainder of Fiscal Year Fair Value Measurements Fair Value Disclosures [Text Block] Schedule of Variable Interest Entities [Table] Variable Interest Entity [Table] Significant Unobservable  Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Encumbered Assets Asset Pledged as Collateral [Member] Supplemental disclosure of cash flow information Supplemental Cash Flow Information [Abstract] Reclassification adjustments on interest rate derivatives recognized in interest expense Amount of Income Reclassified from AOCI into Interest Expense on Statement of Operations Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Investments in real estate joint ventures Real Estate Joint Venture [Line Items] Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities PEO Name PEO Name 2.75%, $600,000 aggregate principal Unsecured Senior Notes Due April 2031 [Member] Unsecured Senior Notes Due April 2031 Geographical [Axis] Geographical [Axis] Restricted cash at beginning of period Restricted cash at end of period Restricted Cash Beginning balance Ending balance Contract with Customer, Liability Total other segment items Segment Reporting, Other Segment Item, Amount Property, Plant and Equipment by Type [Axis] Long-Lived Asset, Class [Axis] Fort Meade/BW Corridor Fort Meade and Baltimore Washington Corridor [Member] Fort Meade and Baltimore Washington Corridor [Member] Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Four Lessee, Operating Lease, Liability, to be Paid, after Year Four Revolving Development Facility Repayments of Secured Debt Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Accounts Receivable, Allowance for Credit Loss [Roll Forward] Accounts Receivable, Allowance for Credit Loss [Roll Forward] Legal Entity [Axis] Legal Entity [Axis] Total Interest Expense, Debt Number of leased operating properties subject to ground lease acquired Number of Leased Operating Properties Subject to Ground Lease Acquired Number of Leased Operating Properties Subject to Ground Lease Acquired Unrealized (loss) income on interest rate derivatives Amount of (Loss) Income Recognized in AOCI on Derivatives Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Prepaid expenses and other assets, net Prepaid Expense and Other Assets Scheduled principal amortization Scheduled Principal Amortization Repayments of Long-term Debt The cash outflow for scheduled principal amortization payments made on debt initially having maturity due after one year or beyond the normal operating cycle, if longer. Cash and cash equivalents and restricted cash at beginning of period Cash and cash equivalents and restricted cash at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Fixed-lease revenue from operating leases Operating Lease, Lease Income, Lease Payments Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Redstone Arsenal Redstone Arsenal [Member] Redstone Arsenal [Member] Effective interest rate Note Receivable, Terms, Effective Interest Rate Note Receivable, Terms, Effective Interest Rate BREIT COPT DC JV LLC BREIT COPT DC JV LLC [Member] BREIT COPT DC JV LLC [Member] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Financing Receivable, Allowance for Credit Loss [Roll Forward] Financing Receivable, Allowance for Credit Loss [Roll Forward] Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Nominal Ownership % Equity Method Investment, Ownership Percentage Share-based compensation Share-Based Payment Arrangement, Noncash Expense Lease costs Lease, Cost Disposal Group Name [Axis] Disposal Group Name [Axis] Schedule of Debt Schedule of Debt [Table Text Block] Weighted average TB-PIUs Unvested TB-PIUs [Member] Unvested TB-PIUs [Member] Investment, Name [Domain] Investment, Name [Domain] Leases Lessee, Operating Leases [Text Block] Unsecured Senior Notes Unsecured Senior Notes [Member] Unsecured Senior Notes 2027 Long-Term Debt, Maturity, Year One Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Schedule of Fair Value and Balance Sheet Classification of Interest Rate Derivatives Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Net income attributable to common shareholders - basic (in dollars per share) Basic EPS attributable to common shareholders (in dollars per share) Earnings Per Share, Basic Deferred revenue associated with operating leases Deferred Revenue Statistical Measurement [Axis] Statistical Measurement [Axis] Insider Trading Arrangements [Line Items] COPT Defense Properties COPT Defense Properties [Member] COPT Defense Properties Schedule of Effect of Interest Rate Derivatives on Consolidated Statements of Operations and Comprehensive Income Derivative Instruments, Gain (Loss) [Table Text Block] Properties in development or held for future development Payments to Develop Real Estate Assets Award Type [Axis] Award Type [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Product and Service [Axis] Product and Service [Axis] Adjustments for changes in fair value of redeemable noncontrolling interest Adjustment for Changes in Fair Value of Redeemable Noncontrolling Interests Adjustment for Changes in Fair Value of Redeemable Noncontrolling Interests Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Revolving Development Facility Proceeds from Issuance of Secured Debt Common Shares Common Stock [Member] Expected volatility of common shares Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Fair Value Measurement [Domain] Fair Value Measurement [Domain] Schedule of Composition of Operating Lease Revenue Operating Lease, Lease Income [Table Text Block] Cost-plus fee Cost-plus Fee Contract [Member] Cost-plus Fee Contract [Member] Property leases - fixed Operating Lease, Cost Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Stock issued for settlement of vested awards (in shares or units) Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period Cover [Abstract] Cover [Abstract] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Noncontrolling Interest [Abstract] Noncontrolling Interest [Abstract] Awards granted, percentage of target award Share-Based Compensation Arrangement by Share-Based Payment Award, Granted, Percentage Of Target Share-Based Compensation Arrangement by Share-Based Payment Award, Granted, Percentage Of Target Interest expense at stated interest rate Interest Expense, Debt, Excluding Amortization Properties under development Properties Under Development [Member] Properties Under Development [Member] Derivative Contract Type [Domain] Derivative Contract [Domain] Beginning balance Ending balance Redeemable Noncontrolling Interest, Equity, Fair Value Term Loan Facility Loans Payable [Member] Number of forms of profit interest units Share-based Compensation Arrangement by Share-based Payment Award, Number of Forms of Executive Compensation Share-based Compensation Arrangement by Share-based Payment Award, Number of Forms of Executive Compensation Equity Awards Adjustments Equity Awards Adjustments [Member] Total liabilities, redeemable noncontrolling interest, and equity Liabilities and Equity Property leases - variable Variable Lease, Cost Employee Stock Option Share-Based Payment Arrangement, Option [Member] Carrying amount and estimated fair value of debt Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Noncontrolling interests in subsidiaries Equity, Attributable to Noncontrolling Interest Unsecured note payable Notes Payable, Other Payables [Member] Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Plan Name [Axis] Plan Name [Axis] Schedule of Investing Receivables Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Stock issued for settlement of vested awards, weighted average grant date fair value (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period, Weighted Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period, Weighted Average Grant Date Fair Value Tabular List, Table Tabular List [Table Text Block] Additional paid-in capital Additional Paid in Capital Interest and other income, net Interest and other income, net Other Nonoperating Income (Expense) Unsecured senior notes Repayments of debt Repayments of Senior Debt Dilutive exchangeable debt (in shares) Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities Number of extensions Debt Instrument, Number Of Extensions Debt Instrument, Number Of Extensions Name Awards Close in Time to MNPI Disclosures, Individual Name Investments in real estate Operating Properties, Net Real Estate Properties [Line Items] Equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Baseline value per common share (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Baseline Common Share Value Represents the baseline common share value that is used in valuing the grant date fair value of awards. Decrease in rents received in advance and security deposits Increase (Decrease) in Advance Rent and Security Deposit Liability The net change in amount that has been received by the entity that represents collections of cash or other assets related to real estate operations revenue for which revenue has not yet been recognized and security deposits. Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest [Abstract] Forfeited (in shares or units) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Schedule of Activity for Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest [Table Text Block] Long-Lived Asset, Class [Domain] Long-Lived Asset, Class [Domain] Investment in UJV with deficit balance Unconsolidated Joint Ventures With Deficit Balances [Member] Unconsolidated Joint Ventures With Deficit Balances LW Redstone Company LLC LW Redstone Company LLC [Member] Represents the investment in L W Redstone Company, LLC, a consolidated joint venture. Adjustment to Compensation: Adjustment to Compensation [Axis] Number of real estate properties Number of Properties Number of Real Estate Properties Properties, net Real Estate Investment Property, Net [Abstract] Net income attributable to noncontrolling interest Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Fixed-rate mortgage debt Fixed Rate Mortgage Debt [Member] A collateralized debt obligation (backed by pledge, mortgage or other lien on the entity's assets) bearing fixed interest rates. Hedging Designation [Domain] Hedging Designation [Domain] Schedule of Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss Schedule of Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss [Table Text Block] Schedule of Credit Losses, Financial Assets and Other Instruments, Allowance for Credit Loss [Table Text Block] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Operating cash flows for finance leases Finance Lease, Interest Payment on Liability Cash paid for interest, net of amounts capitalized Interest Paid, Excluding Capitalized Interest, Operating Activity Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Interest rate swaps designated as cash flow hedges Interest Rate Cash Flow Hedge Liability at Fair Value Variable-rate secured debt Variable Rate Secured Debt [Member] Variable Rate Secured Debt Hedging Designation [Axis] Hedging Designation [Axis] Common Units Common Units [Member] Common units representing ownership interest in the operating partnership. Interest rate swap, effective February 1, 2023 3.742 % Interest Rate Swap, Effective February 2023 3.742% [Member] Interest Rate Swap, Effective February 2023 3.742% Earned performance-based awards payout granted on 25th percentile rank Share-based Compensation Arrangement by Share-based Payment Award of Earned, Payout Percentage Based on Percentile Rank Equals to 25 Represents the earned payout, as a percentage of units granted, if the entity's total shareholder return relative to a peer group of companies ranks at the 25th percentile. Credit Facility [Axis] Credit Facility [Axis] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Name Measure Name Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Other Other Other Operating Segment [Member] Other Other Noncash Income (Expense) Data Center Shells Data Center Shells [Member] Data Center Shells [Member] Debt Debt Instrument [Line Items] Investments in sales-type leases, net Investment in sales-type lease, after allowance Sales-Type Lease, Net Investment in Lease, Excluding Accrued Interest, after Allowance for Credit Loss Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Adjustments to noncontrolling interests resulting from changes in ownership of CDPLP Noncontrolling Interest, Increase (Decrease) From Changes In Ownership Noncontrolling Interest, Increase (Decrease) From Changes In Ownership Additional Paid-in Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Defense/IT Portfolio Defense/IT Portfolio [Member] Defense/IT Portfolio M Square Associates, LLC M Square Associates LLC [Member] Represents the investment in M Square Associates, LLC, a consolidated joint venture. Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Cash and Cash Equivalent Property Finance Leases Finance Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract] Nominal Ownership % Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage Company Selected Measure Amount Company Selected Measure Amount Variable-rate debt Variable Rate Debt [Member] Variable Rate Debt Schedule of Reconciliation of NOI from Real Estate Operations for Reportable Segments and NOI from Service Operations to Net Income Segment Reporting, Reconciliation of Profit (Loss) by Segment to Consolidated [Table Text Block] Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures [Abstract] Depreciation and other amortization Depreciation, Depletion and Amortization Lease incentives, net Incentive to Lessee UJV NOI allocable to COPT Defense UJV NOI allocable to COPT Defense UJV NOI allocable to COPT Defense included in equity in income of unconsolidated entities Unconsolidated Joint Venture Net Operating Income Allocable to Parent Unconsolidated Joint Venture Net Operating Income Allocable to Parent Entity Address, Address Line Two Entity Address, Address Line Two Land Acquisition Land Acquisition [Member] Land Acquisition Share-based compensation issuance, net of redemptions (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Real Estate [Abstract] Real Estate [Abstract] Recognition of finance lease right-of-use assets and related lease liabilities Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Adjustments to noncontrolling interests resulting from changes in CDPLP ownership Equity Change Adjustments to Additional Paid in Capital Reallocation of Minority Interest Adjustments to additional paid in capital as a result of a reallocation of a subsidiary's stockholders' equity to noncontrolling interest due to the subsidiary issuing stock. This reallocation is from a capital transaction. Operating leases, weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Proceeds from sales of properties Proceeds from Sale, Real Estate, Held-for-Investment Non-PEO NEO Non-PEO NEO [Member] Unsecured Senior Notes Senior Notes [Member] Comprehensive income Comprehensive Income (Loss), Net of Tax, After Redeemable Noncontrolling Interest Adjustments Comprehensive Income (Loss), Net of Tax, After Redeemable Noncontrolling Interest Adjustments Entity Address, Address Line One Entity Address, Address Line One Recognition of operating lease right-of-use assets and related lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Vested (in dollars per share or unit) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Income tax expense Income tax expense Income Tax Expense (Benefit) Construction contract and other service expenses Construction contract and other service expenses Construction Contract And Other Service Expenses Construction Contract And Other Service Expenses Deferred leasing costs (net of accumulated amortization of $45,102 and $44,127, respectively) Deferred Initial Direct Cost, Lease, after Accumulated Amortization Operating properties, net Operating properties, net Rental Properties Credit Agreement Credit Agreement [Member] Credit Agreement Distributions to noncontrolling interests in other consolidated entities Minority Interest (Decrease) from Distributions Including Joint Ventures Decrease in noncontrolling interest balance as a result of distributions to equity interests owned by noncontrolling shareholders, partners, or other equity holders in joint ventures included in the entity's consolidated financial statements. Award Timing Method Award Timing Method [Text Block] Net decrease in cash and cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Anne Arundel County, Maryland Anne Arundel County, Maryland [Member] Anne Arundel County, Maryland [Member] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Other investing loans receivable Other Investing Loans Receivables [Member] Other Investing Loans Receivables Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Balance Sheet Location [Axis] Location, Statement of Financial Position, Balance [Axis] Statement [Table] Statement [Table] 2025 Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year Non-operating property assets Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member] Restatement Determination Date: Restatement Determination Date [Axis] Change in Accounts Receivable Change in Accounts Receivable [Abstract] Change in Accounts Receivable Schedule of Accounts Receivable, Contract Assets and Contract Liabilities Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Change in Contract with Customer, Liability Change in Contract with Customer, Liability [Abstract] Sales-type lease interest income Sales-type and Direct Financing Leases, Interest Income Common units in CDPLP Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Nonredeemable Floating Rate Index (over SOFR) Derivative, Basis Spread on Variable Rate Unconsolidated Real Estate Joint Ventures Unconsolidated Real Estate Joint Ventures [Member] Unconsolidated Real Estate Joint Ventures [Member] Schedule of Property Right-of-use Assets and Lease Liabilities Right-of-Use Assets and Lease Liabilities [Table Text Block] Right-of-Use Assets and Lease Liabilities [Table Text Block] Revenues Revenues [Abstract] Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Numerator Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract]