RSUs granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period 2023 Long-term and Short-term Debt, Maturity, Year Two Long-term and Short-term Debt, Maturity, Year Two Summarized Stock Option Activity Schedule of Stock Options Roll Forward [Table Text Block] Document Type Document Type Receivable Type [Axis] Receivable Type [Axis] Options outstanding, Aggregate intrinsic value (in dollars) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Other income (expense) Other Nonoperating Income (Expense) Repayments and settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Options granted Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Schedule of Financial Assets And Liabilities From Variable Interest Entities Schedule of Variable Interest Entities [Table Text Block] Related Party [Axis] Related Party [Axis] Payable to investors Increase (Decrease) In Payable To Investors Increase (Decrease) In Payable To Investors Warrants to purchase common stock Warrants to Purchase Common Stock [Member] Warrants to Purchase Common Stock Vested, Weighted average grant date fair value per share (in dollars 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 Fair Value, Inputs, Level 3 Fair Value, Inputs, Level 3 [Member] Net income before income taxes Income (Loss), Including Portion Attributable to Noncontrolling Interest, before Tax Loan premium and loan trailing fees recognized Loan Premium Fees and Loan Trailing Fees Loan Premium Fees and Loan Trailing Fees 10% adverse change Sensitivity Analysis of Fair Value, Assets, Impact of 10 Percent Adverse Change in Expected Credit Loss Rates Sensitivity Analysis of Fair Value, Assets, Impact of 10 Percent Adverse Change in Expected Credit Loss Rates Statistical Measurement [Domain] Statistical Measurement [Domain] Liabilities and Stockholders’ Equity Liabilities and Equity [Abstract] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Return of capital to interests in consolidated VIEs Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Loan servicing liabilities Fair value, beginning balance Fair value, ending balance Loan servicing liabilities (at fair value) Servicing Liability at Fair Value, Amount Proceeds from borrowings Proceeds from Issuance of Debt Security Exchange Name Security Exchange Name Sales and marketing Selling and Marketing Expense [Member] Income from operations Operating Income (Loss) Changes in fair value recorded in earnings Servicing Liability At Fair Value, Gain (Loss) Included In Earnings Servicing Liability At Fair Value, Gain (Loss) Included In Earnings Sale of loans Servicing Liability at Fair Value, Additions Stock warrants issued, required repurchase amount in event of IPO Class of Warrant or Right, Company Repurchase Requirement Amount Class of Warrant or Right, Company Repurchase Requirement Amount Variable Rate [Domain] Variable Rate [Domain] Deposits Deposits Assets Variable Rate [Axis] Variable Rate [Axis] Cash and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect [Abstract] Assets Assets [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Servicing Asset at Fair Value, Amount [Roll Forward] Servicing Asset at Fair Value, Amount [Roll Forward] Award vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Furniture and fixtures Furniture and Fixtures [Member] Entity Address, State or Province Entity Address, State or Province RSUs vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Cash paid for amounts included in the measurement of lease liabilities Operating Lease, Payments 200 basis point increase Sensitivity Analysis of Fair Value, Assets, Impact of 200 Basis Point Increase In Discount Rates Sensitivity Analysis of Fair Value, Assets, Impact of 200 Basis Point Increase In Discount Rates Financial Asset, Period Past Due [Axis] Financial Asset, Period Past Due [Axis] Greater Than 10% Stockholders Greater Than 10% Stockholders [Member] Greater Than 10% Stockholders Accumulated deficit Retained Earnings (Accumulated Deficit) Operating lease right of use assets Operating Lease, Right-of-Use Asset Unamortized debt discount Debt Instrument, Unamortized Discount Servicing Liabilities at Fair Value Rollforward Schedule of Servicing Liabilities at Fair Value [Table Text Block] 2022 Lessee, Operating Lease, Liability, to be Paid, Year One Rollforward Of Level 3 Assets Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Balances at December 31, 2020 Balances at March 31, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number 2025 Lessee, Operating Lease, Liability, to be Paid, Year Four 2022 Long-term and Short-term Debt, Maturity, Year One Long-term and Short-term Debt, Maturity, Year One Other changes Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Other Increase (Decrease) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Other Increase (Decrease) Remainder of 2021 Long-term and Short-term Debt, Maturity, Remainder Of The Fiscal Year Long-term and Short-term Debt, Maturity, Remainder Of The Fiscal Year Fair Value Sensitivity of Loan Servicing Assets And Liabilities to Adverse Changes in Key Assumptions Schedule of Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets [Table Text Block] Customer [Axis] Customer [Axis] Loan Held For Sale Loan Held For Sale [Member] Loan Held For Sale Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Immediate resale to investors Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Immediate Resale to Investors Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Immediate Resale to Investors Risk retention funding loans Risk Retention Funding Loans [Member] Risk Retention Funding Loans Total operating expenses Operating Expenses Paycheck Protection Program Loan, CARES Act Paycheck Protection Program Loan, CARES Act [Member] Paycheck Protection Program Loan, CARES Act Options exercisable, Number of options Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Stockholder ownership (percent) Share-based Compensation Arrangement by Share-based Payment Award, Options, Stockholder Ownership Share-based Compensation Arrangement by Share-based Payment Award, Options, Stockholder Ownership Fair value of options vested during period Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value Liability Class [Axis] Liability Class [Axis] ISOs Incentive Stock Option [Member] Incentive Stock Option Options cancelled and forfeited Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Revenue from fees, net Revenue from Contract with Customer, Excluding Assessed Tax Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Purchases of loans Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Accrued expenses and other liabilities at fair value Accrued Expenses And Other Liabilities, Fair Value Disclosure Accrued Expenses And Other Liabilities, Fair Value Disclosure Concentration risk (in percent) Concentration Risk, Percentage Business Acquisition [Axis] Business Acquisition [Axis] Income (expense) on warrants and other non-operating expenses, net Income (Expense) On Warrants And Other Non-Operating Expenses, Net Income (Expense) On Warrants And Other Non-Operating Expenses, Net 2020 Equity Incentive Plan 2020 Equity Incentive Plan [Member] 2020 Equity Incentive Plan Servicing Liabilities at Fair Value [Line Items] Servicing Liabilities at Fair Value [Line Items] Purchase period Share-Based Compensation Arrangement By Share-based Payment Award, Purchase Period Share-Based Compensation Arrangement By Share-based Payment Award, Purchase Period Statement [Line Items] Statement [Line Items] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Class of Stock [Domain] Class of Stock [Domain] Computer equipment Computer Equipment [Member] Purchase of notes receivable and residual certificates Payments to Acquire Notes Receivable Measurement Input Type [Domain] Measurement Input Type [Domain] Statement [Table] Statement [Table] Total payments due Outstanding borrowings Total Long-term and Short-term Debt, Gross Long-term and Short-term Debt, Gross Statistical Measurement [Axis] Statistical Measurement [Axis] Credit Facility [Axis] Credit Facility [Axis] Servicing Liability at Fair Value, Amount [Roll Forward] Servicing Liability at Fair Value, Amount [Roll Forward] Aggregate Fair Value and Principal Outstanding of All Loans and Loans 90 days or More Past Due Financing Receivable, Past Due [Table Text Block] Schedule of shares and warrants reserved for issuance Schedule of Class of Stock and Warrants or Rights [Table Text Block] Schedule of Class of Stock and Warrants or Rights Total Common Stock and Class of Warrant or Right, Reserved for Future Issuance Common Stock and Class of Warrant or Right, Reserved for Future Issuance Expected volatility, minimum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum Stock warrants issued, exercise price (in dollars per share) Class of Warrant or Right, Exercise Price of Warrants or Rights Weighted Average Weighted Average [Member] Schedule of Borrowings [Line Items] Schedule of Borrowings [Line Items] Schedule of Borrowings [Line Items] Servicing fees, net Servicing Fees, Net [Member] Servicing Fees, Net Entity Small Business Entity Small Business Basis of Consolidation Consolidation, Policy [Policy Text Block] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Shares sold in offering Sale of Stock, Number of Shares Issued in Transaction Borrowings Debt Disclosure [Text Block] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Gain (loss) on loan servicing arrangements and sale of noncontrolling interests, net Gain (Loss) On Loan Servicing Arrangements And Sale Of Noncontrolling Interests, Net Gain (Loss) On Loan Servicing Arrangements And Sale Of Noncontrolling Interests, Net Options exercisable, Weighted average remaining contractual term Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items] Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items] Capitalized cost amortization term Capitalized Contract Cost, Amortization Period Expected credit loss rates on underlying loans Expected Credit Loss Rate [Abstract] Expected Credit Loss Rate Net proceeds from sale of loans held-for-sale Proceeds from Sale of Loans Held-for-sale Interest income Interest and Dividend Income, Operating Financial Asset, Period Past Due [Domain] Financial Asset, Period Past Due [Domain] Loans held-for-investment Loans Held-For-Investment, Fair Value Disclosure Loans Held-For-Investment, Fair Value Disclosure Amendment Flag Amendment Flag Schedule of Net Income Per Share Attributable to Common Stockholders Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Fair value, beginning balance Fair value, ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Number of shares authorized (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Prodigy Software, Inc. Prodigy Software, Inc. [Member] Prodigy Software, Inc. Engineering and product development Engineering And Product Development [Member] Engineering And Product Development Repayments of borrowings Repayments of debt Repayments of Debt Balance Sheet Components Supplemental Balance Sheet Disclosures [Text Block] Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Operating Activities Entity Central Index Key Entity Central Index Key Related Party [Domain] Related Party [Domain] Proceeds from immediate resale of loans to investors Proceeds From Immediate Resale Of Loans Proceeds From Immediate Resale Of Loans Assets And Liabilities Measure At Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Maximum Exposure to Losses Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Change in fair value of financial instruments (includes $(4,335) to related parties for the three months ended March 31, 2020) Change in fair value of financial instruments Increase (Decrease) in Financial Instruments Used in Operating Activities Financing Receivable, Past Due [Table] Financing Receivable, Past Due [Table] Other Assets [Abstract] Subsequent Events Subsequent Events [Text Block] Customer One Customer 1 [Member] Customer 1 Average effect of fair value of hypothetical 20% adverse change in expected credit loss rates (in percent) Sensitivity Analysis of Fair Value, Assets, Impact of 20 Percent Adverse Change in Expected Credit Loss Rates, Average Sensitivity Analysis of Fair Value, Assets, Impact of 20 Percent Adverse Change in Expected Credit Loss Rates, Average Discount rate Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Discount Rate Net proceeds from sale of loans held-for-investment Proceeds from Sale of Loans Held-for-investment Renewal term Lessee, Operating Lease, Renewal Term Unrecognized stock-based compensation expense related to unvested stock options Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount Statement of Cash Flows [Abstract] Customer operations Customer Operations [Member] Customer Operations Weighted-average effect of dilutive securities (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Collection agency fees Collection Agency Fees [Member] Collection Agency Fees ESPP Employee Stock [Member] Changes in fair value recorded in earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Number of options to renew Lessee, Operating Lease, Number Of Renewal Options Lessee, Operating Lease, Number Of Renewal Options Income Statement Location [Axis] Income Statement Location [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Income Statement Location [Domain] Income Statement Location [Domain] Stock-based compensation expense APIC, Share-based Payment Arrangement, Option, Increase for Cost Recognition 2023 Lessee, Operating Lease, Liability, to be Paid, Year Two Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Operating Lease Expense And Supplemental Cash and Non-Cash Information Lease, Cost [Table Text Block] Majority-owned Affiliates Majority Owned Affiliates [Member] Majority Owned Affiliates 2024 Lessee, Operating Lease, Liability, to be Paid, Year Three Plan Name [Axis] Plan Name [Axis] Other liabilities Other Liabilities Prepayment rate Measurement Input, Prepayment Rate [Member] Issuance of common stock upon settlement of restricted stock units (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Total assets Assets Assets Related Party Transactions Related Party Transactions Disclosure [Text Block] Issuances Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances Ownership interest sold Disposal Group, Ownership Interest Sold Disposal Group, Ownership Interest Sold Trailing fees liability, measurement input Trailing Fees Liability, Measurement Input Trailing Fees Liability, Measurement Input Unvested at December 31, 2020 Unvested at March 31, 2021 Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Title of 12(b) Security Title of 12(b) Security Disposal Group Classification [Axis] Disposal Group Classification [Axis] Public Stock Offering Public Stock Offering [Member] Public Stock Offering Accrued Expenses and Other Liabilities Schedule of Accrued Liabilities [Table Text Block] Weighted average grant date fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Subsequent Event Type [Axis] Subsequent Event Type [Axis] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Annual increase, percent of outstanding shares (percent) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized, Annual Increase, Percent Of Outstanding Shares Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized, Annual Increase, Percent Of Outstanding Shares Prepayment rate Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Prepayment Speed Other assets at fair value Other Assets, Fair Value Disclosure Interest expense Interest Expense Net proceeds from sale of stock Sale of Stock, Consideration Received on Transaction Depreciation and amortization Depreciation, Depletion and Amortization Accrued expenses Accrued Liabilities Product and Service [Axis] Product and Service [Axis] Interest income and fair value adjustments, net (includes $608 from related parties expense and $4,335 of related parties fair value adjustments for the three months ended March 31, 2020) Revenue Not from Contract with Customer Total liabilities Liabilities Liabilities Warrants to purchase common stock Class of Warrant or Right, Unissued Period of recognition Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Less: Present value adjustment Lessee, Operating Lease, Liability, Undiscounted Excess Amount Options vested and expected to vest, Weighted average remaining contractual term Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Net income attributable to common stockholders, basic and diluted Net Income (Loss) Available to Common Stockholders, Basic Commitments and Contingencies Disclosure [Abstract] Total interest income and fair value adjustments, net Interest Income And Fair Value Adjustment, Net Interest Income And Fair Value Adjustment, Net Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Discount rates Discount Rate [Abstract] Discount Rate Stock warrants issued, termination period after company IPO price is confirmed (in dollars per share) Class of Warrant or Right, Repurchase Option, Termination Period After Company's Share Price is Confirmed Class of Warrant or Right, Repurchase Option, Termination Period After Company's Share Price is Confirmed Upstart Network Trust Upstart Network Trust [Member] Upstart Network Trust Warehouse Entities Warehouse Entity [Member] Warehouse Entity Net fair value and accrued interest adjustments Financing Receivable, Allowance for Credit Loss Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items] Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items] Loan servicing assets Fair value, beginning balance Fair value, ending balance Loan servicing assets (at fair value) Servicing Asset at Fair Value, Amount Loan receivable, measurement input Loans Receivable, Measurement Input Loans Receivable, Measurement Input Debt Instrument [Axis] Debt Instrument [Axis] Additional Paid-in Capital Additional Paid-in Capital [Member] Other assets (includes $6,831 and $8,734 at fair value as of December 31, 2020 and March 31, 2021, respectively) Total other assets Other Assets Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Class of Stock [Line Items] Class of Stock [Line Items] Asset Class [Axis] Asset Class [Axis] 2012 Equity Incentive Plan 2012 Equity Incentive Plan [Member] 2012 Equity Incentive Plan Adjustments to reconcile net income to net cash (used in) provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Trailing Fee Liabilities Trailing Fee Liabilities [Member] Trailing Fee Liabilities Revenue from Contract with Customer [Abstract] Common Stock, outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Income Tax Disclosure [Abstract] Variable lease payments Variable Lease, Cost Revolving credit facility Revolving Credit Facility [Member] Principal payments received for loans held by consolidated securitizations Proceeds from Principal Repayments On Loans Held By Consolidated Securitizations Proceeds from Principal Repayments On Loans Held By Consolidated Securitizations Securitizations and Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Short-term Debt [Line Items] Short-term Debt [Line Items] Engineering and product development Research and Development Expense 20% market-servicing rates increase Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 20 Percent Increase In Market-Servicing Rates Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 20 Percent Increase In Market-Servicing Rates Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Subsequent Event Subsequent Event [Member] Options outstanding, Weighted average exercise price per share - December 31, 2020 (in dollars per share) Options outstanding, Weighted average exercise price per share - March 31, 2021 (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Letter of credit outstanding Letters of Credit Outstanding, Amount Common stock, authorized (in shares) Common Stock, Shares Authorized Concentration Risk Type [Axis] Concentration Risk Type [Axis] Borrowings Total borrowings Debt, Long-term and Short-term, Combined Amount Total property, equipment, and software Property, Plant and Equipment, Gross Proceeds from exercise of stock options Proceeds from Stock Options Exercised UNI credit facility UNI Credit Facility [Member] UNI Credit Facility Platform and referral fees, net Platform And Referral Fees, Net [Member] Platform And Referral Fees, Net Sale of loans Servicing Asset at Fair Value, Additions Notes receivable and residual certificates (at fair value) Notes Receivable And Residual Certificates [Member] Notes Receivable And Residual Certificates Schedule of Borrowings [Table] Schedule of Borrowings [Table] Schedule of Borrowings [Table] Prepaid expenses Prepaid Expense Income Statement [Abstract] Required service period Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period Purchase of loans held-for-investment Payments to Acquire Loans Held-for-investment Over-Allotment Option Over-Allotment Option [Member] Schedule of Collection Agency And Borrower Fees Schedule Of Fees And Commissions [Table Text Block] Schedule Of Fees And Commissions Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] 2018-2 RR Financing Agreement 2018-2 RR Financing Agreement [Member] 2018-2 RR Financing Agreement Use of Estimates Use of Estimates, Policy [Policy Text Block] Stock warrants issued, termination period after closing qualified sale Class of Warrant or Right, Repurchase Option, Termination Period After Closing of Qualified Sale Class of Warrant or Right, Repurchase Option, Termination Period After Closing of Qualified Sale Servicing Assets at Fair Value [Line Items] Servicing Assets at Fair Value [Line Items] Loans Held For Investment Loans Held For Investment [Member] Loans Held For Investment Consolidated Entities [Axis] Consolidated Entities [Axis] Exercise of common stock warrant (in shares) Stock Issued During Period, Shares, Warrants Exercised Stock Issued During Period, Shares, Warrants Exercised Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Reclassification of loans from HFI to HFS Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Reclassification Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Reclassification Accounts payable Increase (Decrease) in Accounts Payable, Trade 10% market-servicing rates increase Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 10 Percent Increase In Market-Servicing Rates Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 10 Percent Increase In Market-Servicing Rates Counterparty Name [Domain] Counterparty Name [Domain] Capitalized software costs Payments for Software Purchase of property and equipment Payments to Acquire Property, Plant, and Equipment City Area Code City Area Code Customer operations Customer Operations Expense Customer Operations Expense Document Period End Date Document Period End Date Related party interest expense Interest Expense, Related Party Shares reserved of common stock for issuance Common Stock, Capital Shares Reserved for Future Issuance Net income before attribution to noncontrolling interests Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Term loans Term Loans [Member] Term Loans Disaggregation of Revenue By Type of Service Disaggregation of Revenue [Table Text Block] Sale of loans Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Accrued payroll Employee-related Liabilities Fair Value Of Classes of Loans Held Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Capitalized stock-based compensation expense Share-based Payment Arrangement, Amount Capitalized Stock-based compensation Share-based Payment Arrangement, Noncash Expense 100 basis point increase Sensitivity Analysis of Fair Value, Assets, Impact of 100 Basis Point Increase In Discount Rates Sensitivity Analysis of Fair Value, Assets, Impact of 100 Basis Point Increase In Discount Rates Cover [Abstract] Measurement Input Type [Axis] Measurement Input Type [Axis] Mezzanine Loan Mezzanine Loan [Member] Mezzanine Loan Servicing fees and other receivables Accrued Fees and Other Revenue Receivable Affiliate Affiliated Entity [Member] Leases Lessee, Operating Leases [Text Block] Fair Value Disclosures [Abstract] Credit Risk Rate Assumption for Fair Value of Assets or Liabilities that relate to Transferor's Continuing Involvement, Expected Credit Losses Fair value, beginning balance Fair value, ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Equity Components [Axis] Equity Components [Axis] Annual increase (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized, Annual Increase Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized, Annual Increase Share-based Payment Arrangement [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Receivables [Abstract] Minimum Minimum [Member] Consolidated Entities [Domain] Consolidated Entities [Domain] Sensitivity Analysis of Fair Value Schedule of Sensitivity Analysis of Fair Value [Table Text Block] Schedule of Sensitivity Analysis of Fair Value Unrecognized stock-based compensation expense Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount 2024 Long-term and Short-term Debt, Maturity, Year Three Long-term and Short-term Debt, Maturity, Year Three Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Loans > 90 Days Past Due Financial Asset, Equal to or Greater than 90 Days Past Due [Member] Net loss attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Rollforward of Level 3 Liabilities Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] Forfeited, Weighted average grant date fair value per share (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Stock Options Fair Value Assumptions Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Entity Interactive Data Current Entity Interactive Data Current 2025 Long-term and Short-term Debt, Maturity, Year Four Long-term and Short-term Debt, Maturity, Year Four Revenue: Revenues [Abstract] Summaries Restricted Stock Unit Activity Share-based Payment Arrangement, Outstanding Award, Activity, Excluding Option [Table Text Block] Fair Value Measurement Fair Value Disclosures [Text Block] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Common Stock and Common Stock Warrants Stockholders' Equity Note Disclosure [Text Block] Repayments and settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Loan purchase obligation Purchase Obligation Fair value and other adjustments, net Fair Value And Other Adjustments, Net Fair Value And Other Adjustments, Net Accounts Receivable Accounts Receivable [Member] Ownership percentage Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage Stock-Based Compensation Share-based Payment Arrangement [Policy Text Block] Customer [Domain] Customer [Domain] Entity Registrant Name Entity Registrant Name Subsequent Event Type [Domain] Subsequent Event Type [Domain] Accounts payable Accounts Payable Statement of Stockholders' Equity [Abstract] Weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Assets Assets, Fair Value Disclosure [Abstract] Repayments received Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Repayments Received Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Repayments Received Stock Appreciation Rights Activity Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward] Stock Options Weighted Average Exercise Price Per Share Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Underwriting discount Payments for Underwriting Expense Warrants to purchase convertible preferred stock Warrants to Purchase Convertible Preferred Stock [Member] Warrants to Purchase Convertible Preferred Stock Maximum advance rate (in percent) Line Of Credit Facility, Maximum Advance Rate Line Of Credit Facility, Maximum Advance Rate Noncash interest expense Paid-in-Kind Interest Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Total undiscounted lease payments Lessee, Operating Lease, Liability, to be Paid Schedule of Assets Pledge as Collateral Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block] Less: noncumulative dividends to preferred stockholders Preferred Stock Dividends, Income Statement Impact Risk free rate, minimum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Sale of Stock [Axis] Sale of Stock [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code ESPP purchase price of common stock, percent of market price Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Disposal Group, Disposed of by Sale, Not Discontinued Operations Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] Cash Cash Significant Unobservable Inputs Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Document Transition Report Document Transition Report Employee Stock Purchase Plan Fair Value Assumptions Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text 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[Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Stock warrants reclassified from liability to equity (in shares) Class of Warrant or Right, Warrants Reclassified from Liability to Equity Class of Warrant or Right, Warrants Reclassified from Liability to Equity Supplemental disclosures of non-cash investing and financing activities Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Fair value adjustments from related parties Fair Value Adjustments, Related Party Fair Value Adjustments, Related Party Subsequent Event [Line Items] Subsequent Event [Line Items] Operating lease liability and right-of-use asset Increase (Decrease) In Operating Lease Liability And Right of Use Asset Increase (Decrease) In Operating Lease Liability And Right of Use Asset Purchase of loans for immediate resale to investors Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchase Of Loans For 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