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performance and service vesting conditions - no grant date established Restricted Stock Units, Performance and Service Based, No Grant Date [Member] Restricted Stock Units, Performance and Service Based, No Grant Date 2025 Restructuring Program 2025 Restructuring Program [Member] 2025 Restructuring Program Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Executive Category: Executive Category [Axis] Goodwill [Roll Forward] Goodwill [Roll Forward] LIABILITIES, REDEEMABLE NON-CONTROLLING INTEREST, AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Intangible Asset, Finite-Lived, Class Intangible Asset, Finite-Lived, Class [Domain] Trade name Trade Names [Member] Proceeds from stock option exercises – redeemable non-controlling interest Noncontrolling Interest, Allocation Of Option Exercise Proceeds To Noncontrolling Interest Holders Noncontrolling Interest, Allocation Of Option Exercise Proceeds To Noncontrolling Interest Holders Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Award Type Award Type [Domain] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Fair Value Measurements Fair Value Disclosures [Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Greg Hughes [Member] Greg Hughes Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Lease terms Lessee, Operating Lease, Term of Contract PEO Name PEO Name Geographical Geographical [Axis] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Cash payments and adjustments Payments for Restructuring Cash, cash equivalents, and restricted cash, beginning of period Cash, cash equivalents, and restricted cash, end of period Total cash, cash equivalents, and restricted cash at end of period shown in the condensed consolidated statements of cash flows Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Intangible Asset, Finite-Lived [Table] Intangible Asset, Finite-Lived [Table] Accounts payable Increase (Decrease) in Accounts Payable Other accrued expenses and current liabilities Other Accrued Liabilities, Current 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] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] Restricted cash included within prepaid expenses and other current assets at end of period Restricted Cash and Cash Equivalent, Current 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] Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument Debt Instrument [Axis] Subsequent Event [Table] Subsequent Event [Table] Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Stock-based compensation capitalized for software development Stock Based Compensation Capitalized For Software Development Stock based compensation capitalized for software development. Long-Term Debt, Type Long-Term Debt, Type [Domain] Basic net income per share attributable to BlackLine, Inc. (in usd per share) Basic net income per share attributable to BlackLine, Inc. 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[Table Text Block] General and administrative General and Administrative Expense Adjustment to Compensation: Adjustment to Compensation [Axis] Net income attributable to redeemable non-controlling interest Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Foreign currency forward contracts Foreign Exchange Forward [Member] Performance adjustment (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Performance Adjustment Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Performance Adjustment Restructuring Costs Restructuring and Related Activities Disclosure [Text Block] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Total assets Assets, Fair Value Disclosure Deferred income taxes Deferred Federal, State and Local, Tax Expense (Benefit) Professional services Technology Service [Member] Name Measure Name Income Taxes Income Tax Disclosure [Text Block] Accounts payable Accounts Payable, Current Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Additional Paid-in Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Capitalized software development costs Payments to Develop Software Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and cash equivalents at end of period Cash and Cash Equivalent Company Selected Measure Amount Company Selected Measure Amount Less comprehensive income attributable to redeemable non-controlling interest: Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest [Abstract] Equity Method Investments and Joint Ventures [Abstract] Equity Method Investments and Joint Ventures [Abstract] Entity Address, Address Line Two Entity Address, Address Line Two Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Current assets: Assets, Current [Abstract] Foreign currency forward contracts Derivative Liability Non-PEO NEO Non-PEO NEO [Member] Senior Notes Senior Notes [Member] Entity Address, Address Line One Entity Address, Address Line One Provision for income taxes Income tax expense Income Tax Expense (Benefit) Total cost of revenues Cost of Product and Service Sold Award Timing Method Award Timing Method [Text Block] Net decrease in cash, cash equivalents, and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Net income attributable to BlackLine, Inc. Net income attributable to BlackLine, Inc., including adjustment to redeemable non-controlling interest Net income attributable to BlackLine, Inc. Net Income (Loss) Attributable to Parent Long-Term Debt, Type Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Statement [Table] Statement [Table] Restatement Determination Date: Restatement Determination Date [Axis] Proceeds from exercises of stock options Proceeds from Stock Options Exercised Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Coupon interest expense Coupon Interest Expense Coupon interest expense. Stock option exercises - redeemable non-controlling interest Stock Issued During Period Value Stock Options Exercised, Redeemable Non-Controlling Interest Stock Issued During Period Value Stock Options Exercised, Redeemable Non-Controlling Interest Debt Instruments [Abstract] Debt Instruments [Abstract] Stock option exercises Stock Issued During Period Value Stock Options Exercised Net Of Shares Withholding Stock issued during period value stock options exercised net of shares withholding. Net foreign currency (gains) losses Unrealized Gain (Loss), Foreign Currency Transaction, before Tax BlackLine K.K. Black Line K K [Member] BlackLine K.K. Basis of Presentation, Significant Accounting Policies, and Recently-Issued Accounting Pronouncements 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]