Supplemental disclosures of cash flow information Supplemental Cash Flow Information [Abstract] Foreign currency transaction gains (losses) Foreign Currency Transaction Gain (Loss), Realized Federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Net loss per share Earnings Per Share, Policy [Policy Text Block] Restricted stock units, Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period State Current State and Local Tax Expense (Benefit) Total leased liabilities Operating And Finance Lease, Lease Liability Operating And Finance Lease, Lease Liability Business credits Deferred Tax Assets, Tax Credit Carryforwards, General Business Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Domain] Leasehold Improvements Leasehold improvements Leasehold Improvements [Member] Net loss attributable to BlackLine, Inc. Net loss attributable to BlackLine, Inc., including adjustment to redeemable non-controlling interest Net loss attributable to BlackLine, Inc. Net Income (Loss) Attributable to Parent Cap price per share Cap Price Per Share Cap price per share. Lease liability, lease not yet commenced, amount Lessee, Lease Liability, Lease Not yet Commenced, Amount Lessee, Lease Liability, Lease Not yet Commenced, Amount Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Marketable securities (amortized cost of $658,886 and $175,211 at December 31, 2021 and December 31, 2020, respectively) Fair Value Debt Securities, Available-for-sale, Current Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards Accrued salaries and employee benefits Employee-related Liabilities, Current Income Statement Location Income Statement Location [Axis] Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Transaction related costs Business Combination, Acquisition Related Costs Statistical Measurement Statistical Measurement [Domain] Segments Segment Reporting, Policy [Policy Text Block] Security Exchange Name Security Exchange Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Information Disclosure [Abstract] Conversion price Debt Instrument, Convertible, Conversion Price Forfeited/canceled (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Revenues Revenue from Contract with Customer [Abstract] Additional paid-in capital Additional Paid in Capital, Common Stock Options, canceled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Operating leases Operating Lease, Weighted Average Remaining Lease Term Foreign currency Foreign Currency Transactions and Translations Policy [Policy Text Block] Supplemental Cash Flow and Other Information Leases, Supplemental Information [Table Text Block] Leases, Supplemental Information Other assets Other assets, total Other Assets, Noncurrent Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Investment from redeemable non-controlling interest Proceeds from Noncontrolling Interests Estimated dividend yield Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Retirement Benefits [Abstract] Retirement Benefits [Abstract] Net increase in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Entity File Number Entity File Number Expected volatility Volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Stock-based compensation APIC, Share-based Payment Arrangement, Increase for Cost Recognition Intangible assets Deferred Tax Liabilities, Intangible Assets Aggregate intrinsic value, exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Change in fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Defensive patent Patented Technology [Member] Noncash lease expense Non Cash Lease Expense Non-cash lease expense. Forfeited/canceled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Schedule of Amortized Cost and Fair Values of Marketable Securities by Remaining Contractual Maturity Debt Securities, Available-for-sale [Table Text Block] Number of single customers comprising 10% or more Number Of Customers Number of customers. Lease option to terminate (within) Lessee, Operating and Finance, Lease Option to Terminate, Period Lessee, Operating and Finance, Lease Option to Terminate, Period Subsequent Event Type [Domain] Subsequent Event Type [Domain] Debt Conversion, Name Debt Conversion, Name [Domain] Noncurrent Lease Liabilities, Noncurrent [Abstract] Lease Liabilities, Noncurrent Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Redeemable Noncontrolling Interest, by Legal Entity [Table] Redeemable Noncontrolling Interest, by Legal Entity [Table] Deferred tax liabilities, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Amortization expenses Amortization of Intangible Assets Business Acquisition, Contingent Consideration [Line Items] Business Acquisition, Contingent Consideration [Line Items] Total leased assets Total Operating Lease and Finance Lease Right-of-Use Assets Total Operating Lease and Finance Lease Right-of-Use Assets Weighted average useful lives Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Increases related to prior year tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Add: Dilutive effect of securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities Variable cost Variable Lease, Cost Leases, remaining lease terms Operating and Finance Lease, Remaining Lease Terms Operating and Finance Lease, Remaining Lease Terms Total shares excluded from net loss per share Conversion option in notes not considered in calculation of diluted net loss per share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Operating leases Operating Lease, Weighted Average Discount Rate, Percent Valuation Allowance [Abstract] Valuation Allowance [Abstract] Maturing between 1 and 2 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, After Year One Through Year Two Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, After Year One Through Year Two Deferred revenue recognized Contract with Customer, Liability, Revenue Recognized Research and development Research and Development Expense [Member] Sale of Stock Sale of Stock [Axis] Liability Class Liability Class [Axis] Subsequent Events [Abstract] Subsequent Events [Abstract] Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table] Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table] Deferred tax assets, net of valuation allowance Deferred Tax Assets, Net of Valuation Allowance Restricted cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Exercise price of options, granted (usd per share) Granted (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Transaction costs allocated to equity component of notes Transaction Costs Attributable To Equity Component Transaction costs allocated to equity component. Business Acquisition Business Acquisition [Axis] Purchase consideration reduced by working capital adjustments Payments to Acquire Businesses, Net of Working Capital Adjustments Payments to Acquire Businesses, Net of Working Capital Adjustments Debt Instruments [Abstract] Debt Instruments [Abstract] Title of Individual Title of Individual [Domain] Property, plant, and equipment, gross Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, before Accumulated Depreciation and Amortization Proceeds from maturities of marketable securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Net change in unrealized gains (losses) on marketable securities, net of tax of $0 for the years ended December 31, 2021, 2020 and 2019 OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Income Tax Examination [Table] Income Tax Examination [Table] Award Type Award Type [Domain] Professional services Technology Service [Member] Summary of Notes Convertible Debt [Table Text Block] Local Phone Number Local Phone Number ASSETS Assets [Abstract] Total Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value Schedule of Investments in Marketable Securities Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Adjustment attributable to non-controlling interest (Note 4) Adjustment to redeemable non-controlling interest Adjustment to redeemable non-controlling interest Noncontrolling Interest, Change in Redemption Value Exercisable at End of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract] Leased assets obtained in exchange for new financing lease liabilities Right-of-Use Asset Obtained in Exchange for Finance Lease Liability 0.125% Convertible Senior Notes Due 2024 Zero Point One Two Five Percent Convertible Senior Notes Due Twenty Twenty Four [Member] Zero point one two five percent convertible senior notes due twenty twenty four. Right-of-use assets, for leases not yet commenced Operating Lease and Finance Lease Right-of-Use Assets, Lease Not Yet Commenced Operating Lease and Finance Lease Right-of-Use Assets, Lease Not Yet Commenced Restricted stock units, Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Intangible Assets and Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Fair Value Finite-lived Intangible Assets Acquired Property and equipment Property, Plant and Equipment, Policy [Policy Text Block] Outstanding Beginning balance (in shares) Outstanding Ending balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Convertible senior notes, consecutive trading days Debt Instrument, Convertible, Threshold Consecutive Trading Days Trade name Trade Names [Member] Accumulated Deficit Retained Earnings [Member] Debt Instrument Debt Instrument [Axis] Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Increase in valuation allowance recorded through earnings Valuation Allowance Deferred Tax Asset Increase In Amount Valuation allowance deferred tax asset increase in amount recorded through earnings Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Accrued expenses and other current liabilities Accrued expenses and other current liabilities, total Accrued Expenses And Other Liabilities Current Accrued expenses and other liabilities, current. Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Finance lease cost: Finance Lease Costs [Abstract] Finance Lease Costs Schedule of Long-lived Assets Which Consist of Property and Equipment, Net and Operating Lease Right-of-use Assets by Geographic Region Long-lived Assets by Geographic Areas [Table Text Block] Estimated fair value of contingent consideration Noncash Financing and Investing Activities, Estimated present Value of Contingent Consideration, Liability Noncash Financing and Investing Activities, Estimated present Value of Contingent Consideration, Liability Accounts receivable Increase (Decrease) in Accounts Receivable Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities at end of period Capital Expenditures Incurred but Not yet Paid Aggregate principal repurchased Debt Instrument, Repurchased Face Amount Leased assets obtained in exchange for new operating lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Significant Components of Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Vesting percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Stock-based compensation capitalized as an asset Share-based Payment Arrangement, Amount Capitalized Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Comprehensive loss Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Financing cash flows from finance leases Finance Lease, Principal Payments Number of operating segments Number of Operating Segments Stock-based compensation Compensation Related Costs, Policy [Policy Text Block] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Basic net loss per share attributable to BlackLine, Inc. (in usd per share) Earnings Per Share, Basic Contingent consideration, current Business Combination, Contingent Consideration, Liability, Current 2024 Lessee, Operating Lease, Liability, to be Paid, Year Three Revenues Revenue from Contract with Customer [Text Block] Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Restricted stock units, Nonvested, Beginning balance (in shares) Restricted stock units, Nonvested, Ending balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Beginning fair value Ending fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Cash paid for amounts included in the measurement of lease liabilities Lessee. Cash Flow [Abstract] Lessee. Cash Flow Capitalized software development costs included in accounts payable and accrued expenses and other current liabilities at end of period Capitalized Software Development Costs Included In Accounts Payable And Accrued Expenses And Other Liabilities Current Capitalized software development costs included in accounts payable and accrued expenses, and other liabilities, current. Schedule of Disaggregation of Revenues by Geographic Region Disaggregation of Revenue [Table Text Block] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Increase (decrease) in valuation allowance recorded through equity Decrease in valuation allowance recorded through equity Valuation Allowance Deferred Tax Asset Increase (Decrease) In Amount Valuation allowance deferred tax asset increase (decrease) in amount recorded through equity. Business interest carryforward Deferred Tax Asset, Interest Carryforward Intangible assets, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Debt Instrument, implied interest rate Debt Instrument, Implied Interest Rate Debt Instrument, Implied Interest Rate Machinery and Equipment Machinery and Equipment [Member] Partial repurchase of convertible senior notes Repayments of Convertible Debt Commercial paper Commercial Paper [Member] Acquisition of common stock for tax withholding obligations Share-based Payment Arrangement, Decrease for Tax Withholding Obligation Maximum number of shares Issuable (in shares) Approved award grants to employees (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Net deferred taxes Deferred Tax Liabilities, Net Operating cash flows from operating lease liabilities Operating Lease, Payments Recaptured dual consolidated losses Effective Income Tax Rate Reconciliation, Recaptured Dual Consolidated Losses, Percent Effective Income Tax Rate Reconciliation, Recaptured Dual Consolidated Losses, Percent Board of Directors, Compensation Committee Board of Directors, Compensation Committee [Member] Board of Directors, Compensation Committee Restricted cash Restricted Cash and Cash Equivalents Additional investment in subsidiary Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Purchase of Interest by Parent Research and development Research and Development Expense, Policy [Policy Text Block] Purchase price consideration Business Combination, Consideration Transferred Provision for (benefit from) credit losses Accounts Receivable, Credit Loss Expense (Reversal) Principal Long-term Debt, Gross Goodwill [Roll Forward] Goodwill [Roll Forward] Entity Voluntary Filers Entity Voluntary Filers Number of leases not yet commenced Lessee, Number of Leases Not Yet Commenced Lessee, Number of Leases Not Yet Commenced Convertible notes Deferred Tax Liabilities, Financing Arrangements Plan Name Plan Name [Axis] Net carrying amount Long-term Debt Finance lease assets Finance Lease, Right-of-Use Asset, after Accumulated Amortization Total assets Assets, Fair Value Disclosure Level 1 Fair Value, Inputs, Level 1 [Member] Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Foreign currency translation attributable to redeemable non-controlling interest Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest Fair Value by Liability Class Fair Value by Liability Class [Domain] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Entity Small Business Entity Small Business Operating Leases Lessee, Operating Lease, Liability, Payment, Due [Abstract] Increases related to current year tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Total liabilities, redeemable non-controlling interest, and stockholders' equity Liabilities and Equity Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Other accrued expenses and current liabilities Other Accrued Liabilities, Current Liabilities: Lease Liabilities [Abstract] Lease Liabilities Other income (expense) Other Income and Expenses [Abstract] Deferred revenue Contract with Customer, Liability, Current 2026 Lessee, Operating Lease, Liability, to be Paid, Year Five Exercised (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Redeemable Noncontrolling Interest, Equity [Roll Forward] Redeemable Noncontrolling Interest, Equity [Roll Forward] Redeemable Noncontrolling Interest, Equity Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] LIABILITIES, REDEEMABLE NON-CONTROLLING INTEREST, AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Accounts payable Increase (Decrease) in Accounts Payable Additions in the period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Transaction costs allocated to liability component of notes Transaction Costs Allocated To Liability Component Transaction costs allocated to liability component. Net Loss per Share Earnings Per Share [Text Block] Operating expenses Operating Expenses [Abstract] Entity Interactive Data Current Entity Interactive Data Current 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Four Minimum Minimum [Member] Stock option exercises (in shares) Stock Issued During Period Shares Stock Options Exercised Net Of Shares Withholdings Stock issued during period shares stock options exercised net of shares withholdings. Carrying amount of equity component Debt Instrument, Convertible, Carrying Amount of Equity Component Change in fair value of contingent consideration Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Right-of-Use and finance lease assets Deferred Tax Liabilities Right Of Use Assets Deferred tax liabilities right of use asset. Gross profit Gross profit Gross Profit 2023 Lessee, Operating Lease, Liability, to be Paid, Year Two Effect of foreign currency exchange rate changes on cash, cash equivalents, and restricted cash Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Initial conversion rate Debt Instrument, Convertible, Conversion Ratio Total liabilities Financial and Nonfinancial Liabilities, Fair Value Disclosure Comprehensive loss attributable to redeemable non-controlling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Forfeited/canceled (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Nondeductible meals and entertainment Effective Income Tax Rate Reconciliation, Nondeductible Expense, Meals and Entertainment, Percent Beginning gross unrecognized tax benefits Ending gross unrecognized tax benefits Unrecognized Tax Benefits Income Tax Authority Income Tax Authority [Domain] Total deferred tax assets Deferred Tax Assets, Gross Convertible Notes Convertible Notes [Member] Convertible notes. Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Gross Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Entity Address, State or Province Entity Address, State or Province Number of executive officers, options granted Number Of Executive Officers Options Granted Number of executive officers, options granted. Business combination, outstanding common stock percentage Business Acquisition, Percentage of Voting Interests Acquired Current liabilities: Liabilities, Current [Abstract] Lease extension period (up to) Lessee, Operating and Finance Lease Extension Period Lessee, Operating and Finance Lease Extension Period Capitalized software development costs Payments to Develop Software Revenue recognition Revenue [Policy Text Block] Restricted cash included within other assets at end of period Restricted cash Restricted Cash and Cash Equivalents, Noncurrent Operating lease liabilities Increase (Decrease) in Operating Lease Liability General and administrative General and Administrative Expense Acquisition, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Convertible Senior Notes Debt Disclosure [Text Block] Beginning Balance (in shares) Ending Balance (in shares) Shares, Outstanding Exercisable at End of period (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Components of Total Provision for Income Taxes Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Equity Awards Share-based Payment Arrangement [Text Block] Operating lease, right-of-use asset, accumulated depreciation Operating Lease, Right-Of-Use Asset, Accumulated Depreciation Operating Lease, Right-Of-Use Asset, Accumulated Depreciation Level 3 Fair Value, Inputs, Level 3 [Member] Leases Lessee, Leases [Policy Text Block] Less: accumulated depreciation and amortization Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, Accumulated Depreciation and Amortization Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Accounting Policies [Abstract] Accounting Policies [Abstract] Weighted Average Remaining Contractual Term (Years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items] Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items] Basis of presentation and summary of significant accounting policies. Percentage of principal amount of notes declared as accrued based on certain customary events of default Percentage Of Principal Amount Of Notes Declared As Accrued Based On Certain Customary Events Of Default Percentage of principal amount of notes declared as accrued based on certain customary events of default. Percentage of employer matching contribution, second tier Defined Contribution Plan Employer Matching Contribution Percent Of Match Second Tier Defined contribution plan employer matching contribution percent of match second tier. Cost of revenues Cost of Revenue [Abstract] Federal Current Federal Tax Expense (Benefit) Total lease obligations Operating Lease, Liability Redeemable non-controlling interest (Note 4) Balance at beginning of period Balance at end of period Redeemable Noncontrolling Interest, Equity, Carrying Amount Document Transition Report Document Transition Report FourQ Systems, Inc. FourQ Systems, Inc. [Member] FourQ Systems, Inc. Net foreign currency (gains) losses Foreign Currency Transaction Gain (Loss), before Tax Common stock, $0.01 par value, 500,000,000 shares authorized, 58,984,247 issued and outstanding at December 31, 2021 and 57,682,118 issued and outstanding at December 31, 2020 Common Stock, Value, Issued Finance leases Finance Lease, Weighted Average Discount Rate, Percent Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Purchase of capped calls Adjustment To Additional Paid In Capital Purchase Of Capped Calls Adjustment to additional paid in capital purchase of capped calls. Weighted-average period to recognize unrecognized compensation expense Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Nonvested at Beginning balance (usd per share) Nonvested at Ending balance (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Less comprehensive loss attributable to redeemable non-controlling interest: Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest [Abstract] Addition from acquisition Goodwill, Acquired During Period Stock options with performance conditions Performance Shares [Member] Commitments and contingencies (Note 15) Commitments and Contingencies Contingent consideration liability payment period Business Combination Contingent Consideration Liability Payment Period Business Combination Contingent Consideration Liability Payment Period Subsequent Event [Table] Subsequent Event [Table] Number of leased properties Lessee, Number of Leases Lessee, Number of Leases Leases Lessee, Operating Leases [Text Block] Summary of Activity in Redeemable Non-Controlling Interest Redeemable Noncontrolling Interest [Table Text Block] Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Emerging Growth Company Entity Emerging Growth Company Amortization of assets Finance Lease, Right-of-Use Asset, Amortization Operating and finance leases Deferred Tax Assets Operating Leases Deferred tax assets, operating leases. Allowances for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Business Combinations Business Combination Disclosure [Text Block] ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag BlackLine Systems, Inc. Black Line Systems Inc [Member] BlackLine Systems Inc. Schedule of Weighted Average Assumptions Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Antidilutive Securities, Name Antidilutive Securities, Name [Domain] Estimated interest rate Debt Instrument, Measurement Input Ownership Ownership [Axis] Foreign Deferred Foreign Income Tax Expense (Benefit) Auditor Name Auditor Name Cover [Abstract] Cover [Abstract] Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Total operating expenses Costs and Expenses Convertible Senior Notes due 2026 Convertible Senior Notes due 2026 [Member] Convertible Senior Notes due 2026 Investments in Marketable Securities Marketable Securities, Policy [Policy Text Block] Lessee Disclosure [Abstract] Lessee Disclosure [Abstract] Accrued expenses and other current liabilities Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities Stock Options and Restricted Stock Units Stock Options And Restricted Stock Units [Member] Stock options and restricted stock units. Deferred tax liability, net Deferred tax liability, net Deferred Tax Liabilities, Deferred Expense, Debt Issuance Costs Cash and cash equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Income Tax Authority Income Tax Authority [Axis] Thereafter Finance Lease, Liability, to be Paid, after Year Five Net change in unrealized gain (losses) on marketable securities, tax OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Financial Instrument [Axis] Financial Instrument [Axis] Total revenues Revenues Revenue from Contract with Customer, Excluding Assessed Tax Defined Contribution Plan Compensation and Employee Benefit Plans, Other than Share-based Compensation [Text Block] Stock-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Less imputed interest Finance Lease, Liability, Undiscounted Excess Amount Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Numerator: Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Stock options with service-only vesting conditions Stock Options Share-based Payment Arrangement, Option [Member] Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Axis] Federal tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Measurement Input Type [Domain] Measurement Input Type [Domain] 2026 Finance Lease, Liability, to be Paid, Year Five Securities in continuous loss position, less than 12 Months, estimated fair value Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Common Stock Common Stock [Member] Interest income Investment Income, Interest International Income (Loss) from Continuing Operations before Income Taxes, Foreign Geographic Information Segment Reporting Disclosure [Text Block] Finance leases Finance Lease, Weighted Average Remaining Lease Term Loss from operations Operating Income (Loss) Matching contributions to plan Defined Contribution Plan, Employer Discretionary Contribution Amount Financed purchases of property and equipment Payments To Finance Property Plant And Equipment Payments to finance property, plant and equipment. Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Operating lease liabilities, current Operating Lease, Liability, Current Gross Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax 2023 Finite-Lived Intangible Asset, Expected Amortization, Year Two Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Document Fiscal Year Focus Document Fiscal Year Focus Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Stock-based compensation Share-based Payment Arrangement, Noncash Expense Additional Paid-in Capital Additional Paid-in Capital [Member] Cash and cash equivalents Cash and cash equivalents at end of period Cash and Cash Equivalents, at Carrying Value Right to purchase shares at fair value at the time of exercise, percentage Right To Purchase Shares At Fair Value At The Time Of Exercise Percentage Right to purchase shares at fair value at the time of exercise percentage. Developed technology Technology-Based Intangible Assets [Member] Summary of Restricted Stock Units Activity Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Cash paid for income taxes Income Taxes Paid Business Combination, Contingent Consideration Arrangements [Abstract] Business Combination, Contingent Consideration Arrangements [Abstract] Asset impairment charges Asset Impairment Charges Other income (expense), net Other Nonoperating Income (Expense) Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Net loss and adjustment attributable to redeemable non-controlling interest (Note 4) Net Income Loss Adjustment Attributable To Redeemable Non Controlling Interest Net income (loss) adjustment attributable to redeemable non-controlling interest. Property and Equipment Property, Plant and Equipment [Member] Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block] Business Combinations [Abstract] Maximum Maximum Maximum [Member] Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Total liabilities Liabilities Deferred tax assets Deferred Tax Assets, Net [Abstract] Award Type Award Type [Axis] 2022 Finite-Lived Intangible Asset, Expected Amortization, Year One Granted (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Aggregate Intrinsic Value, Outstanding at Beginning of period Aggregate Intrinsic Value, Outstanding at End of period Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Deferred Tax Asset Valuation Allowance [Roll Forward] Deferred Tax Asset Valuation Allowance [Roll Forward] Deferred Tax Asset Valuation Allowance Schedule of Maturities of Lease Liabilities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Measurement Input Type [Axis] Measurement Input Type [Axis] Total stockholders' equity Beginning Balance Ending Balance Stockholders' Equity Attributable to Parent Equity component of partial repurchase of 2024 convertible senior notes Adjustment to additional paid in capital for equity component of partial repurchase of notes Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments Capitalized software development costs, net Capitalized Software Development Costs for Software Sold to Customers Net operating loss carryforwards Operating Loss Carryforwards Common stock, shares issued (in shares) Common Stock, Shares, Issued City Area Code City Area Code Restricted cash included within prepaid expenses and other current assets at end of period Restricted Cash and Cash Equivalents, Current Prepaid expenses and other current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets Enterprise Zone Enterprise Zone [Member] Enterprise zone. 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Business day Debt Instrument, Convertible, Threshold, Business Day Debt Instrument, Convertible, Threshold, Business Day Operating lease right-of-use assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Operating Lease Right-Of-Use Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Operating Lease Right-Of-Use Assets Intangible assets Intangible Assets, Finite-Lived, Policy [Policy Text Block] International Non-US [Member] Subsequent Events Subsequent Events [Text Block] Foreign currency translation Temporary Equity, Foreign Currency Translation Adjustments Lease, Cost [Abstract] Lease, Cost [Abstract] Amortization Expense by Operation Expense Categories Finite-lived Intangible Assets Amortization Expense [Table Text Block] Comprehensive loss attributable to BlackLine, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Unaudited Quarterly Data Quarterly Financial Information [Text Block] Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Denominator: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Net (loss) attributable to redeemable non-controlling interest (excluding adjustment to non-controlling interest) Net Income (Loss) Excluding Portion Attributable To Redeemable Noncontrolling Interest Net income loss excluding portion attributable to redeemable noncontrolling interest. Convertible Senior Notes Debt, Policy [Policy Text Block] Deferred tax liabilities, net Deferred Income Tax Liabilities, Net Option to purchase principal amount Debt Instrument Face Amount Optional Debt instrument face amount optional. 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Issuance of common stock through employee stock purchase plan Stock Issued During Period, Value, Employee Stock Purchase Plan Measurement Input, Credit Spread Measurement Input, Credit Spread [Member] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Vested (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value General and administrative General and Administrative Expenses General and Administrative Expense [Member] Principles of consolidation and basis of presentation Consolidation, Policy [Policy Text Block] Entity Shell Company Entity Shell Company Deferred customer contract acquisition costs Deferred Policy Acquisition Cost Expected term (years) Expected term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Total current liabilities Liabilities, Current Employee Stock Purchase Plan ("ESPP") Employee Stock [Member] Acquisition of common stock for tax withholding obligations Payment, Tax Withholding, Share-based Payment Arrangement Business combination, contribution Business combination, payable at closing Payments to Acquire Businesses, Gross Summary of Changes in Valuation Allowance Summary of Valuation Allowance [Table Text Block] Condition One Condition One [Member] Condition one member. Money market funds Money Market Funds [Member] Cash and cash equivalents Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Employer matching contribution, percent of employees' gross pay Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Ownership Ownership [Domain] Current Fiscal Year End Date Current Fiscal Year End Date Unamortized debt discount and issuance costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Rimilia Rimilia Holdings Ltd. [Member] Rimilia Holdings Ltd. 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Statistical Measurement Statistical Measurement [Axis] Number of common stock entitled to receive upon vesting of award (in shares) Share Based Compensation Arrangement By Share Based Payment Award Number Of Common Stock Entitled To Receive Upon Vesting Of Award Share based compensation arrangement by share based payment award, number of common stock entitled to receive upon vesting of award. 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