Schedule of Available-for-sale Securities Debt Securities, Available-for-Sale [Table Text Block] Target Units (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Awards Expected To Issue Share-Based Compensation Arrangement By Share-Based Payment Award, Awards Expected To Issue Stock option exercises, net Stock Issued During Period, Value, Stock Options Exercised, Net of Taxes Paid Stock Issued During Period, Value, Stock Options Exercised, Net of Taxes Paid Award Timing Predetermined Award Timing Predetermined [Flag] Amortization of premium on acquired deposits Amortization Of Fair Value Premium On Acquired Deposits Amortization Of Fair Value Premium On Acquired Deposits Entity File Number Entity File Number Additional paid-in capital Additional Paid-in Capital [Member] Interest-bearing deposit accounts: Interest-Bearing Deposit Liabilities [Abstract] Tabular List, Table Tabular List [Table Text Block] Interest and fee income on loans: Interest and Fee Income, Loans and Leases [Abstract] Accounting Pronouncements Recently Adopted and Recent Accounting Pronouncements Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Loans charged off Financing Receivable, Allowance for Credit Loss, Writeoff SOFR Secured Overnight Financing Rate (SOFR) [Member] Schedule of Estimated Fair Values of Financial Instruments Not Carried at Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Maximum potential amount of future payments required under the commitments Guarantor Obligations, Maximum Exposure, Undiscounted Available-for-sale securities Debt Securities [Member] Other comprehensive income: Other Comprehensive Income (Loss), Tax [Abstract] Measurement Basis [Axis] Measurement Basis [Axis] Adjustment to Compensation: Adjustment to Compensation [Axis] Estimated Fair Value Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Restricted stock activity, net of forfeitures (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Common Equity Tier 1 (CET 1) to risk-weighted assets, For Capital Adequacy Purposes, Ratio Banking Regulation, Common Equity Tier 1 Risk-Based Capital Ratio, Capital Adequacy, Minimum Adjustment to Compensation, Amount Adjustment to Compensation Amount Share-based compensation expense Share-Based Payment Arrangement, Noncash Expense Total borrowing capacity with the FHLB Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available Outstanding Notional Derivative Asset, Notional Amount Option awards Share-Based Payment Arrangement, Option [Member] Trust preferred securities, aggregate liquidation valuation amount Common Stock Held in Assets Common Stock Held in Assets Taxable Interest And Dividend Income, Securities, Operating, Taxable Interest And Dividend Income, Securities, Operating, Taxable Public finance Public Finance Finance Leases Portfolio Segment [Member] Asset Pledged as Collateral without Right Asset Pledged as Collateral without Right [Member] Total stockholders’ equity Balance, beginning of year Balance, ending of year Equity, Attributable to Parent Measurement Frequency [Axis] Measurement Frequency [Axis] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Insider Trading Policies and Procedures [Line Items] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Assets: Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Fair Value, Recurring Fair Value, Recurring [Member] Tier 1 leverage capital to average assets, To be Well-Capitalized under Prompt Corrective Action Provisions, Amount Banking Regulation, Tier 1 Leverage Capital, Well Capitalized, Minimum Liabilities 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Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Schedule of Deferred Compensation Arrangement with Individual, Share-based Payments [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Substandard - Nonaccrual Substandard Nonaccrual [Member] Substandard Nonaccrual Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Financing Receivable, Credit Quality Indicator [Table] Financing Receivable, Credit Quality Indicator [Table] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Tier 1 leverage capital to average assets, Actual Ratio Banking Regulation, Tier 1 Leverage Capital Ratio, Actual Interest and dividend income on securities: Interest and Dividend Income, Securities, by Taxable Status [Abstract] Revolving Loans Converted to Term Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan Amortization of core deposits and other intangible assets Amortization of Other Intangible Assets Amortization of Other Intangible Assets Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Share-Based Payment Arrangement, Performance Shares, Activity Share-Based Payment Arrangement, Performance Shares, Activity [Table Text Block] Remaining lease term Lessee, Operating Lease, Remaining Lease Term Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Total interest expense Interest expense Interest Expense, Operating Due within 1 year Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, Year One Document Fiscal Period Focus Document Fiscal Period Focus Award Timing Method Award Timing Method [Text Block] Nonaccrual Financing Receivable, Excluding Accrued Interest, Nonaccrual Total available-for-sale Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss Award Type [Axis] Award Type [Axis] Schedule of Dividends Payable Schedule of Dividends Payable [Table Text Block] Parent Company Parent Company [Member] Trading Symbol Trading Symbol 2030 Lessee, Operating Lease, Liability, to be Paid, Year Four Accrued expenses and other liabilities Accrued Liabilities and Other Liabilities Entity Address, City or Town Entity Address, City or Town Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Greater than $250 Time Deposits, at or Above FDIC Insurance Limit Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Loans pledged to the FHLB Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged Commitments including funding of fixed-rate loans Loans and Leases Receivable, Commitments, Fixed Rates Maturities of Time Deposits [Abstract] Maturities of Time Deposits [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Common Equity Tier 1 (CET 1) to risk-weighted assets, Actual Ratio Banking Regulation, Common Equity Tier 1 Risk-Based Capital Ratio, Actual Schedule of Held-to-maturity Securities Debt Securities, Held-to-Maturity [Table Text Block] Changes in operating assets and liabilities: Increase (Decrease) in Operating Assets [Abstract] Unrealized Losses Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Outstanding, beginning of period (in shares) Outstanding, vested, and exercisable, end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number 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] Unfunded Loan Commitment Unfunded Loan Commitment [Member] Schedule of Unpaid Principal Loan Balance of Servicing Portfolio Schedule Of Unpaid Principal Loan Balance Of Servicing Portfolio [Table Text Block] Schedule Of Unpaid Principal Loan Balance Of Servicing Portfolio Costs related to the issuance of the subordinated notes Debt Issuance Costs, Net Recorded gain (loss) on banking derivative Derivative, Gain (Loss) on Derivative, Net Certificates of deposit Interest Expense, Time Deposits Total noninterest income Noninterest Income Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Gross Unrealized Losses Gross Unrealized Losses Debt Securities, Held-to-Maturity, Accumulated Unrecognized Loss Noninterest expense: Noninterest Expense [Abstract] Class of Financing Receivable [Domain] Class of Financing Receivable [Domain] Loans Greater than 90 Days Past Due, Still Accruing Financing Receivable, Excluding Accrued Interest, 90 Days or More Past Due, Still Accruing 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] Derivative Instruments and Hedging Activities Disclosure [Abstract] Due after 1 year through 5 years Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Rate Debt Instrument, Interest Rate, Effective Percentage Pledged Status [Domain] Pledged Status [Domain] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Provision for income taxes Provision for income taxes Income Tax Expense (Benefit) Interest rate margin on variable rate basis Debt Instrument, Basis Spread on Variable Rate Government National Mortgage Association Government National Mortgage Association (GNMA) [Member] Balance, beginning of year Balance, end of year Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Document Information [Line Items] Document Information [Line Items] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Derivative financial instruments designated as hedging instruments: Designated as Hedging Instrument [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Servicing fees Contractually Specified Servicing Fees, Amount Due within 1 year Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Fixed-rate interest Loans and Leases Receivable, Commitments, Fixed Interest Rate Loans and Leases Receivable, Commitments, Fixed Interest Rates Other noninterest income Noninterest Income, Other Operating Income Outstanding, beginning of period (in shares) Outstanding, end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number First Foundation First Foundation [Member] First Foundation Commitments and Contingencies Disclosure [Abstract] Total unrecognized compensation cost related to non-vested stock options granted Unrecognized Compensation Cost Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Securities available-for-sale, at fair value Estimated Fair Value Total available-for-sale Debt Securities, Available-for-Sale, Excluding Accrued Interest Proceeds from sales of other real estate owned and foreclosed assets Proceeds from Sale of Other Real Estate Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Subsequent Event Subsequent Event [Member] Net interest income Interest Income (Expense), Operating Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Tier 1 risk-based capital to risk-weighted assets, Actual Amount Banking Regulation, Tier 1 Risk-Based Capital, Actual Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Pioneer's Option Plans Pioneer's Option Plans [Member] Pioneer's Option Plans Dividends, term without prior regulatory approval, preceding period of net income Dividends, Term Without Prior Regulatory Approval, Preceding Period of Net Income Dividends, Term Without Prior Regulatory Approval, Preceding Period of Net Income Mortgage Operations Mortgage Operations Segment [Member] Mortgage Operations Segment Equity Components [Axis] Equity Components [Axis] Entity Ex Transition Period Entity Ex Transition Period Three years before current year Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year Sublease income Sublease Income Standby Letters of Credit Standby Letters of Credit [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Number of reportable segments Number of Reportable Segments Commercial real estate: Commercial Real Estate [Member] Entity Address, State or Province Entity Address, State or Province Substandard - Accruing Substandard [Member] Total interest income Interest income Interest and Dividend Income, Operating Special Mention Special Mention [Member] Financial Asset, Aging [Domain] Financial Asset, Aging [Domain] Loans (excluding collateral dependent loans) Loans Receivable, Fair Value Disclosure Other Other Derivative Financial Instruments [Member] Other Derivative Financial Instruments Individual: Individual [Axis] Probable Units (in shares) Stock Issued During Period, Shares, Probable Units Stock Issued During Period, Shares, Probable Units Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Tier 1 risk-based capital to risk-weighted assets, For Capital Adequacy Purposes, Amount Banking Regulation, Tier 1 Risk-Based Capital, Capital Adequacy, Minimum Entity Interactive Data Current Entity Interactive Data Current Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract] Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract] Financing Receivable, Troubled Debt Restructuring [Line Items] Financing Receivable, Modified [Line Items] Interest income: Interest and Dividend Income, Operating [Abstract] Total noninterest expense Noninterest Expense Interest paid on deposits Noncash Investing And Financing Activities, Interest Paid On Deposits Noncash Investing And Financing Activities, Interest Paid On Deposits Net loss (gain) on other real estate owned and foreclosed assets activity Net Gain (Loss) on Other Real Estate Owned and Foreclosed Assets Net Gain (Loss) on Other Real Estate Owned and Foreclosed Assets Payment Delay / Deferral Payment Deferral [Member] Interest expense on deposits Total interest-bearing deposit accounts Interest Expense, Deposits Federal Home Loan Bank stock dividends Federal Home Loan Bank Stock Dividends Federal Home Loan Bank Stock Dividends Noninterest income: Noninterest Income [Abstract] Entity Central Index Key Entity Central Index Key PEO Name PEO Name 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] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Schedule of Amortized Costs by Segment of Loans and Credit Risk Profile of Loan Portfolio Financing Receivable Credit Quality Indicators [Table Text Block] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Origination of loans held-for-sale Payment for Origination, Loan, Mortgage, Held-for-Sale Tier 1 leverage capital to average assets, For Capital Adequacy Purposes, Amount Banking Regulation, Tier 1 Leverage Capital, Capital Adequacy, Minimum Noninterest-bearing accounts Noninterest-bearing deposit accounts Noninterest-Bearing Deposit Liabilities Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] First Anniversaries Share-Based Payment Arrangement, Tranche One [Member] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Exercise Price Award Exercise Price New Mexico Banquest Capital Trust I (NMBCT I) New Mexico Banquest Capital Trust I (NMBCT I) [Member] New Mexico Banquest Capital Trust I (NMBCT I) Entity Filer Category Entity Filer Category Tier 1 risk-based capital to risk-weighted assets, For Capital Adequacy Purposes, Ratio Banking Regulation, Tier 1 Risk-Based Capital Ratio, Capital Adequacy, Minimum Class of Stock [Domain] Class of Stock [Domain] Unrecognized share-based compensation cost related to unvested restricted stock units Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Subsequent Event Type [Axis] Subsequent Event Type [Axis] Treasury management service fees Treasury Management Service Fees Treasury Management Service Fees Amount of cumulative income (loss) in fair value hedging adjustment Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease) Collateral Dependent Loans with No Related Allowance, Amortized Cost Financing Receivable, With No Related Allowance, Amortized Cost Financing Receivable, With No Related Allowance, Amortized Cost Interest-bearing deposit accounts: Interest Expense, Deposits [Abstract] Vesting [Domain] Vesting [Domain] 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] Entity Address, Address Line One Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Two Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] Accrued expenses and other liabilities Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Revolving Loans Converted to Term Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan, Writeoff Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Proceeds from the sale or redemption of other investments Proceeds from Sale and Maturity of Other Investments Fair Value as of Grant Date Award Grant Date Fair Value Four years before current fiscal year Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year Schedule of Advances and Other Borrowings Outstanding Schedule of Long-Term Debt Instruments [Table Text Block] Salary and employee benefits Salary and employee benefits Labor and Related Expense Derivative Instruments and Hedging Activities Disclosures [Table] Derivative Instruments and Hedging Activities Disclosures [Table] Stock-based awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Tier 1 leverage capital to average assets, For Capital Adequacy Purposes, Ratio Banking Regulation, Tier 1 Leverage Capital Ratio, Capital Adequacy, Minimum Issued (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Document Quarterly Report Document Quarterly Report Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Tier 1 risk-based capital to risk-weighted assets, Actual Ratio Banking Regulation, Tier 1 Risk-Based Capital Ratio, Actual Deposits Deposit Liabilities Disclosures [Text Block] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Unrealized Losses Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 2028 Lessee, Operating Lease, Liability, to be Paid, Year Two Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term LIBOR London Interbank Offered Rate [Member] London Interbank Offered Rate Loans Insured or Guaranteed by Government Authorities [Domain] Loans Insured or Guaranteed by Government Authorities [Domain] Total collateral dependent loans Financing Receivable, Impaired, Fair Value Disclosure Financing Receivable, Impaired, Fair Value Disclosure Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Prepaid expenses and other assets Prepaid Expense and Other Assets Payments to acquire businesses Payments to Acquire Businesses, Gross Non-PEO NEO Non-PEO NEO [Member] Intrinsic value of the stock options Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Federal Home Loan Bank advances Amount Advance from Federal Home Loan Bank Outstanding Notional Derivative Liability, Notional Amount FirstSun Capital Bancorp 2017 Equity Incentive Plan FirstSun Capital Bancorp 2017 Equity Incentive Plan [Member] FirstSun Capital Bancorp 2017 Equity Incentive Plan $100 through $250 Time Deposits, $100,000 Through $250,000 Time Deposits, $100,000 Through $250,000 Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Award Type [Domain] Award Type [Domain] 2027 Lessee, Operating Lease, Liability, to be Paid, Year One Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Compensation Amount Outstanding Recovery Compensation Amount Total risk-based capital to risk-weighted assets, To be Well-Capitalized under Prompt Corrective Action Provisions, Amount Banking Regulation, Total Risk-Based Capital, Well Capitalized, Minimum Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Estimated Fair Value Estimate of Fair Value Measurement [Member] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Due after 1 year through 5 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Weighted Average Shares Weighted Average Number of Shares Outstanding Reconciliation [Abstract] 2030 Time Deposit Maturities, Year Four Less than $100 Time Deposits, Less than $100,000 Financing Receivable, Past Due [Line Items] Financing Receivable, Past Due [Line Items] Due after 5 years through 10 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Accumulated other comprehensive loss, net Accumulated Other Comprehensive Income (Loss), Net of Tax Financial Instruments [Domain] Financial Instruments [Domain] Due after 10 years Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Award Date [Domain] Award Date [Domain] April 2023 April 2023 [Member] April 2023 Performance-based restricted stock Performance Shares [Member] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Banking Regulation, Regulatory Capital Requirement, Compliance [Table] Minimum Minimum [Member] Net interest income after credit loss expense Interest Income (Expense), after Provision for Loan Loss Federal Reserve Bank stock Federal Reserve Bank Advances [Member] Company Selected Measure Name Company Selected Measure Name Fair Value Measurement [Domain] Fair Value Measurement [Domain] Total risk-based capital to risk-weighted assets, For Capital Adequacy Purposes, Amount Banking Regulation, Total Risk-Based Capital, Capital Adequacy, Minimum Debt Debt Disclosure [Text Block] Impairment of other real estate owned and foreclosed assets Impairment Of Other Real Estate Owned And Foreclosed Assets Impairment Of Other Real Estate Owned And Foreclosed Assets Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Due after 10 years Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year 10 Net income available to common stockholders, diluted (in shares) Net income applicable to common stockholders, diluted Net Income (Loss) Available to Common Stockholders, Diluted Fourth Anniversaries Share Based Compensation Award Tranche Four [Member] Share Based Compensation Award Tranche Four [Member] Collateral Held [Domain] Collateral Held [Domain] Demand and NOW Interest Expense, Demand Deposit Accounts And Negotiable Order Of Withdrawal (NOW) Deposits Accounts Interest Expense, Demand Deposit Accounts And Negotiable Order Of Withdrawal (NOW) Deposits Accounts Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Second Anniversaries Share-Based Payment Arrangement, Tranche Two [Member] Weighted average diluted common shares (in shares) Weighted Average Number of Shares Outstanding, Diluted Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms Derivative [Table] Derivative [Table] Schedule of Servicing and Ancillary Fees from Mortgage Servicing Portfolio Schedule Of Servicing And Ancillary Fees From Servicing Assets [Table Text Block] Schedule Of Servicing And Ancillary Fees From Servicing Assets Entity Small Business Entity Small Business Federal Home Loan Bank Federal​ Home ​Loan ​Bank [Member] Federal​ Home ​Loan ​Bank Income Tax Disclosure [Abstract] Amortized Cost Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity [Abstract] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Document Transition Report Document Transition Report Due after 1 year through 5 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date Trust and investment advisory fees Trust and investment advisory fees Investment Banking Revenue Income Taxes Income Tax Disclosure [Text Block] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Fair value of derivatives in a net liability position Derivative, Net Liability Position, Aggregate Fair Value Short-term leases Short-Term Lease, Cost Document Type Document Type Level 3 Fair Value, Inputs, Level 3 [Member] Earnings Per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Loss Contingencies [Table] Loss Contingencies [Table] Additional paid-in capital Additional Paid in Capital Revolving Financing Receivable, Excluding Accrued Interest, Revolving, Writeoff Regulatory Capital Requirements under Banking Regulations [Abstract] Regulatory Capital Requirements under Banking Regulations Proceeds from sales of loans held-for-sale Proceeds from Sale, Loan, Held-for-Sale Statistical Measurement [Axis] Statistical Measurement [Axis] Financial Instruments Subject to Mandatory Redemption, Financial Instrument [Domain] Financial Instruments Subject to Mandatory Redemption, Financial Instrument [Domain] Year before current fiscal year, writeoffs Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Proceeds from Federal Home Loan Bank advances Proceeds from FHLBank Borrowings, Financing Activities Net income available to common stockholders, basic (in shares) Net income applicable to common stockholders, basic Net Income (Loss) Available to Common Stockholders, Basic Mortgage banking services, net Mortgage banking services, net Fees and Commissions, Mortgage Banking and Servicing Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Weighted-Average Remaining Term (years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract] Combination Term Extension and Interest Rate Reduction Extended Maturity and Interest Rate Reduction [Member] Schedule of Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Table Text Block] Level 1 Fair Value, Inputs, Level 1 [Member] Line of credit outstanding Long-Term Line of Credit Mortgage servicing rights resulting from sale or securitization of mortgage loans Mortgage Servicing Rights Resulting From Sale Or Securitization Of Mortgage Loans Mortgage Servicing Rights Resulting From Sale Or Securitization Of Mortgage Loans Repayments of Federal Home Loan Bank advances Payments of FHLBank Borrowings, Financing Activities Recorded loss on mortgage banking derivative liabilities Mortgage Banking Derivative Liability [Member] Mortgage Banking Derivative Liability Diluted (in dollars per share) Diluted earnings per common share (in dollars per share) Earnings Per Share, Diluted Multifamily Multifamily [Member] Non-cash investing and financing activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Due after 5 years through 10 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Loans, modified in period, amount Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount Multifamily Multifamily Loans [Member] Multifamily Loans Loans held-for-sale, at fair value Financing Receivable, Held-for-Sale Consolidation Items [Domain] Consolidation Items [Domain] Investments, Debt and Equity Securities [Abstract] Servicing resulting from transfers of financial assets Servicing Asset at Fair Value, Additions Term Extension Extended Maturity [Member] FHLB advances Federal Home Loan Bank Borrowings, Fair Value Disclosure Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Number of Transactions Derivative Asset, Number of Instruments Held Imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Proceeds from the sale or redemption of restricted equity securities Proceeds from Sale of Equity Securities, FV-NI 2027 Time Deposit Maturities, Year One Cash paid for income taxes, net Income Taxes Paid, Net April 2025 April 2025 [Member] April 2025 Lease right-of-use assets Increase (Decrease) In Lease Right-of-Use Asset Increase (Decrease) In Lease Right-of-Use Asset Total undiscounted operating lease liability Lessee, Operating Lease, Liability, to be Paid Dividends from Sunflower Wealth Advisors, LLC Subsidiaries [Member] Schedule of Actual and Required Capital Amounts Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Total loans Total Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss Nature of Operations Nature Of Operations [Policy Text Block] Nature Of Operations Securities sold under agreements to repurchase Securities Sold under Agreements to Repurchase Fee income Gain (Loss) on Derivative Instruments, Net, Pretax Schedule of Fair Value and Unrealized Losses on Debt Securities in Continuous Unrealized Loss Position Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Expiration Date Trading Arrangement Expiration Date Certificates of deposit: Time Deposits [Abstract] Common Equity Tier 1 (CET 1) to risk-weighted assets, To be Well-Capitalized under Prompt Corrective Action Provisions, Ratio Banking Regulation, Common Equity Tier 1 Risk-Based Capital Ratio, Well Capitalized, Minimum Financing Receivable, Unpaid Principal Balance Of Servicing Portfolio [Table] Financing Receivable, Unpaid Principal Balance Of Servicing Portfolio [Table] Financing Receivable, Unpaid Principal Balance Of Servicing Portfolio Decrease in fair value of mortgage servicing rights Mortgage Servicing Rights (MSR) Impairment (Recovery) Net unrealized (loss) gain on securities available-for-sale Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Premises and equipment, net Property, Plant and Equipment, Net Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Construction and land Construction and land Construction Loans [Member] Entity Current Reporting Status 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Net Change In Unrealized Gain (Loss) On Available For Sale Securities And Unrealized Gain On Fair Value Hedges Of Securities Available-For-Sale Total liabilities and stockholders’ equity Liabilities and Equity Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Accounting Policies [Abstract] Schedule of Future Minimum Leases Payment Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Purchase of other investments Payments to Acquire Other Investments Current fiscal year Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year Pay vs Performance Disclosure [Line Items] Lease liability (included in accrued expenses and other liabilities in our consolidated balance sheets) Total operating lease liability included in the accompanying balance sheet Operating Lease, Liability Tier 1 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Information [Abstract] Other Performance Measure, Amount Other Performance Measure, Amount Weighted-Average Exercise Price, per Share Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Derivative Instrument [Axis] Derivative Instrument [Axis] Vesting [Axis] Vesting [Axis] Liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Commercial real estate Commercial Real Estate Owner occupied Commercial Real Estate Portfolio Segment [Member] Deferred fees, costs, premiums and discounts on loan portfolio Financing Receivable, Unamortized Loan Cost (Fee) and Purchase Premium (Discount) Entity [Domain] Entity [Domain] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Schedule of Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Axis] Schedule of Financial Instruments Subject to 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treasury US Treasury Securities [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Available-for-sale: Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] Doubtful Doubtful [Member] Purchases, issuances, sales and settlements: Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract] Other debt Other Debt Obligations [Member] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Loans Receivable Loans Receivable [Member] Deferred tax assets, net Deferred Income Tax Assets, Net Depreciation and amortization on premises and equipment Depreciation, Depletion and Amortization Mortgage backed - residential Residential Mortgage-Backed Securities [Member] Accrued interest receivable Interest Receivable, Fair Value Disclosure Interest Receivable, Fair Value Disclosure Loan originations, net of repayments Loan Originations, Net Of Repayments Loan Originations, Net Of Repayments Arrangement Duration Trading Arrangement Duration Financing Receivable, Unpaid Principal Balance Of Servicing Portfolio [Line Items] Financing Receivable, Unpaid Principal Balance Of Servicing Portfolio [Line Items] Financing Receivable, Unpaid Principal Balance Of Servicing Portfolio Segments [Axis] Segments [Axis] Local Phone Number Local Phone Number Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Stockholders' Equity Share-Based Payment Arrangement [Text Block] Assets Assets [Abstract] Credit Facility [Axis] Credit Facility [Axis] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Debt Instrument [Axis] Debt Instrument [Axis] Forfeited (in dollars per share) 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[Member] Subordinated Debt Related To Trust Preferred Securities Name Trading Arrangement, Individual Name Underlying Asset Class [Domain] Underlying Asset Class [Domain] Expected volatility, number of comparable companies Share-based Compensation Arrangement By Share-based Payment Award, Fair Value Assumptions, Expected Volatility, Number Of Comparable Companies Share-based Compensation Arrangement By Share-based Payment Award, Fair Value Assumptions, Expected Volatility, Number Of Comparable Companies Schedule of Short-term Debt [Table] Short-Term Debt [Table] Loans held-for-sale Loan, Held-for-Sale, Fair Value Disclosure Debt instrument, face amount Debt Instrument, Face Amount Name Awards Close in Time to MNPI Disclosures, Individual Name Collateral Dependent Loans with Allowance, Amortized Allowance Financing Receivable, With Related Allowance, Amortized Cost Financing Receivable, With Related Allowance, Amortized Cost Outstanding, beginning of period (in dollars per share) 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Interest Expense, Operating and Nonoperating [Abstract] FirstSun Capital Bancorp 2021 Equity Incentive Plan FirstSun Capital Bancorp 2021 Equity Incentive Plan [Member] FirstSun Capital Bancorp 2021 Equity Incentive Plan [Member] Purchases of available-for-sale securities Payments to Acquire Debt Securities, Available-for-Sale Statistical Disclosure for Banks [Abstract] Preferred stock, $0.0001 par value, 10,000,000 shares authorized, none issued or outstanding, respectively Preferred Stock, Value, Issued Obligations of states and political subdivisions US States and Political Subdivisions Debt Securities [Member] Accrued interest payable Interest Payable Subordinated debt, net Subordinated Debt Year before current fiscal year Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year Subordinated Debt Subordinated Debt [Member] Financial Asset, Aging [Axis] Financial Asset, Aging [Axis] All Executive Categories All Executive Categories [Member] Common stock, $0.0001 par value; 80,000,000 and 50,000,000 voting shares authorized, respectively; 27,935,888 and 27,887,337 voting shares issued and outstanding, respectively; 20,000,000 and zero non-voting shares authorized, respectively; No non-voting shares issued and outstanding, respectively Common Stock, Value, Issued Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Exchange ratio (in shares) Business Combination, Consideration Transferred, Equity Interests Issued and Issuable, Entity Shares Issued Per Acquiree Share Business Combination, Consideration Transferred, Equity Interests Issued and Issuable, Entity Shares Issued Per Acquiree Share Business acquisition, equity interest issued Business Combination, Consideration Transferred, Equity Interest, Share Issued, Value Commitments and contingencies (Note 15) Commitments and Contingencies Current fiscal year, writeoffs Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff Tax exempt Interest And Fee Income Loans And Leases, Tax Exempt Interest And Fee Income Loans And Leases, Tax Exempt Fixed rate term advance Federal Home Loan Bank Advances, Fixed Rate [Member] Federal Home Loan Bank Advances, Fixed Rate Business Combination [Axis] Business Combination [Axis] Short-term Debt [Line Items] Short-Term Debt [Line Items] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Total Servicing Assets, Unpaid Principal Loan Balance Servicing Assets, Unpaid Principal Loan Balance Due after 10 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Restricted Stock Award Restricted Stock Award [Member] Restricted Stock Award Loans 60-89 Days Past Due Financial Asset, 60 to 89 Days Past Due [Member] Hedging Designation [Axis] Hedging Designation [Axis] Other interest income Other Interest and Dividend Income Derivative Contract [Domain] Derivative Contract [Domain] Financing Receivable, Allowance for Credit Loss [Table] Financing Receivable, Allowance for Credit Loss [Table] Proceeds from issuance of common stock, net of issuance costs and taxes paid on cashless exercise of equity awards Proceeds from Issuance of Common Stock Late and ancillary fees Late And Ancillary Fee Income Generated By Servicing Financial Assets, Amount Late And Ancillary Fee Income Generated By Servicing Financial Assets, Amount All Individuals All Individuals [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Purchases of premises and equipment Payments to Acquire Property, Plant, and Equipment Name Forgone Recovery, Individual Name Award contractual term Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period 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] Other noninterest expenses Other Noninterest Expense, Including Amortization Of Intangible Assets Other Noninterest Expense, Including Amortization Of Intangible Assets Allowance for credit losses Debt Securities, Allowance For Credit Losses Debt Securities, Allowance For Credit Losses Four years before current fiscal year, writeoffs Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff Schedule of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Commercial and industrial Commercial and Industrial Commercial Portfolio Segment [Member] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Title of 12(b) Security Title of 12(b) Security Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Provision for credit losses (Benefit) provision for credit losses Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal) Earnings per share: Earnings Per Share [Abstract] Non-owner occupied Non-owner occupied Non-Owner Occupied Loans [Member] Non-Owner Occupied Loans Non-voting Common Stock Nonvoting Common Stock [Member] Interest expense on securities sold under agreements to repurchase Interest Expense, Securities Sold under Agreements to Repurchase Changes in fair value: Servicing Asset at Fair Value, Changes in Fair Value [Abstract] Servicing Asset at Fair Value, Changes in Fair Value Interest paid on borrowed funds Noncash Investing And Financing Activities, Interest Paid On Borrowed Funds Noncash Investing And Financing Activities, Interest Paid On Borrowed Funds Schedule of Interest Expense Incurred on Deposits Interest Income and Interest Expense Disclosure [Table Text Block] Two years before current fiscal year, writeoffs Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff Amortization and impairment of intangible assets Amortization of intangible assets Amortization and Impairment of Intangible Assets Amortization and Impairment of Intangible Assets Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Effect of dilutive securities Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Financing Receivable, Allowance for Credit Loss [Line Items] Financing Receivable, Allowance for Credit Loss [Line Items] Exercised (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Total Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset Award Timing Disclosures [Line Items] Measurement Frequency [Domain] Measurement Frequency [Domain] Federal Home Loan Bank stock Federal Home Loan Bank Advances [Member] Lease renewal term Lessee, Operating Lease, Renewal Term Net change in securities sold under agreements to repurchase Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase Loan Restructuring Modification [Domain] Loan Restructuring Modification [Domain] Loans, net of allowance for credit losses of $82,955 and $85,016, respectively Loans, net of allowance for credit losses Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss Net income Net income Net Income (Loss) Attributable to Parent Total risk-based capital to risk-weighted assets, Actual Ratio Banking Regulation, Total Risk-Based Capital Ratio, Actual Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Adoption Date Trading Arrangement Adoption Date Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Financing Receivable, Past Due [Table] Financing Receivable, Past Due [Table] Collateral Dependent Loans with Allowance, Related Allowance Financing Receivable, With Related Allowance, Related Allowance Financing Receivable, With Related Allowance, Related Allowance Line of Credit Line of Credit [Member] Retained earnings Retained Earnings (Accumulated Deficit) Money market Deposits, Money Market Deposits Residential real estate Residential Real Estate Residential real estate Residential Portfolio Segment [Member] 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] Discount rate Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Discount Rate Due to changes in valuation inputs or assumptions used in the valuation model Servicing Asset at Fair Value, Changes in Fair Value Resulting from Changes in Valuation Inputs or Changes in Assumptions Increase in cash surrender value of bank-owned life insurance Life Insurance, Corporate or Bank Owned, Change in Value Class of Stock [Axis] Class of Stock [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subordinated Notes Due January 15, 2032 Subordinated Notes Due January 15, 2032 [Member] Subordinated Notes Due January 15, 2032 [Member] 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] Total other real estate owned and foreclosed assets, net: Other Real Estate Owned And Foreclosed Assets, Net, Fair Value Disclosure Other Real Estate Owned And Foreclosed Assets, Net, Fair Value Disclosure Statement [Table] Statement [Table] Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Variable Rate [Domain] Variable Rate [Domain] Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Fiscal Year Maturity [Abstract] Number of Transactions Derivative Liability, Number of Instruments Held Schedule of Reconciliation for Level 3 Assets Measured at Fair Value on a Recurring Basis Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] All Adjustments to Compensation All Adjustments to Compensation [Member] Interest Rate Reduction Contractual Interest Rate Reduction [Member] Amendment Flag Amendment Flag Estimated Fair Value Debt Securities, Available-for-Sale, Fair Value, Fiscal Year Maturity [Abstract] Aggregate shares of common stock (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Transfers and Servicing [Abstract] Termination Date Trading Arrangement Termination Date Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] 2029 Time Deposit Maturities, Year Three Allowance for credit losses Loans, allowance for credit losses Balance, beginning of period Balance, end of period Total Collateral Dependent Loans, Related Allowance Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest Subordinated debt, net Subordinated Debt Obligations, Fair Value Disclosure Third Anniversaries Share-Based Payment Arrangement, Tranche Three [Member] Weighted Average Rate - Operating Leases Operating Lease, Weighted Average Discount Rate, Percent Schedule of Stock Option Activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Weighted average common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Schedule of Computation of Basic and Diluted Earnings Per Share of Common Stock Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Composition of Deposits Deposit Liabilities, Type [Table Text Block] Subsequent Events [Abstract] Segment Reporting [Abstract] Debt Disclosure [Abstract] Schedule of Non-vested Restricted Stock Schedule of Unvested Restricted Stock Units Roll Forward [Table Text Block] Additional borrowing availability with the FHLB Federal Home Loan Bank, Advances, General Debt Obligations, Amount of Available, Unused Funds Other Financial Institutions Other Financial Institutions [Member] Other Financial Institutions Debt discount on the convertible notes Debt Instrument, Unamortized Discount Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Consolidated Entities [Axis] Consolidated Entities [Axis] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Derivative Instruments and Hedging Activities Disclosures [Line Items] Derivative Instruments and Hedging Activities Disclosures [Line Items] Schedule of Weighted-Average key Assumptions Used to Estimate Fair Value of Mortgage Servicing Rights Schedule Of Fair Value Assumptions, Servicing Assets [Table Text Block] Schedule Of Fair Value Assumptions, Servicing Assets Use of Estimates Use of Estimates, Policy [Policy Text Block] Total risk-based capital to risk-weighted assets, Actual Amount Banking Regulation, Total Capital, Actual Payments of dividends Payments of Dividends Other comprehensive (loss) income Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Occupancy, equipment and software Occupancy, equipment and software Occupancy, Net Subsequent Events Subsequent Events [Text Block] Insider Trading Arrangements [Line Items] Prior Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] Loans Not Past Due Financial Asset, Not Past Due [Member] Held-to-maturity: Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss [Abstract] Total liabilities Liabilities FirstSun Capital Bancorp 2017 And 2021 Equity Incentive Plan FirstSun Capital Bancorp 2017 And 2021 Equity Incentive Plan [Member] FirstSun Capital Bancorp 2017 And 2021 Equity Incentive Plan % of Total Class of Loans Financing Receivable, Excluding Accrued Interest, Modified in Period, to Total Financing Receivables, Percentage Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Thereafter Time Deposit Maturities, after Year Four Time Deposit Maturities, after Year Four Standby letters of credit commitment Fair Value Disclosure, off-Balance-Sheet Risks, Amount, Liability Proceeds from pay-downs, sales or maturities of available-for-sale securities Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Savings Deposits, Savings Deposits Other real estate owned and foreclosed assets, net Other Real Estate, Foreclosed Assets, and Repossessed Assets Consolidation Items [Axis] Consolidation Items [Axis] Variable Rate [Axis] Variable Rate [Axis] Proceeds from maturities of held-to-maturity securities Proceeds from Maturities, Prepayments and Calls of Held-to-Maturity Securities Securities held-to-maturity, fair value of $29,045 and $29,446, respectively Total held-to-maturity Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Federal Home Loan Mortgage Corporation Federal Home Loan Mortgage Corporation (FHLMC) [Member] Posted collateral aggregate fair value Collateral Already Posted, Aggregate Fair Value