Document And Entity Information Note To Financial Statement Details Textual Significant Accounting Policies Note 2 - Significant Accounting Policies and Consolidated Financial Statement Components Global intangible low-taxed income Percentage of the difference between reported income tax expense (Benefit) And expected income tax expense (Benefit) Computed by applying the domestic federal statutory income tax rates to pretax income (Loss) From continuing operations attributable to global intangible low-taxed income. Note 3 - Segment Reporting Note 5 - Investment in Equity-method Investee Note 6 - Fair Values of Assets and Liabilities Note 7 - Property Note 8 - Leases Note 9 - Notes Payable Note 10 - Convertible Senior Notes Income Tax Disclosure [Text Block] Note 12 - Income Taxes Note 13 - Net Income (Loss) Attributable to Controlling Interests Per Common Share Note 14 - Stock-based Compensation Note 2 - Significant Accounting Policies and Consolidated Financial Statement Components - Summary of Allowance for Uncollectible Loans and Fees Receivable (Details) Note 2 - Significant Accounting Policies and Consolidated Financial Statement Components - Summary of Aging of Delinquent Loans and Fees Receivable (Details) Note 2 - Significant Accounting Policies and Consolidated Financial Statement Components - Summary of Troubled Debt Restructurings (Details) Schedule of Debt [Table Text Block] Credit Card Receivable [Member] Note 2 - Significant Accounting Policies and Consolidated Financial Statement Components - Summary of Fees and Related Income on Earning Assets (Details) Note 2 - Significant Accounting Policies and Consolidated Financial Statement Components - Components of Revenue from Contracts with Customers (Details) Note 3 - Segment Reporting - Summary of Operating Segment Information (Details) Note 5 - Investment in Equity-method Investee - Summary of Equity-method Investee (Details) Note 6 - Fair Values of Assets and Liabilities - Summary of Fair Value Hierarchy for Assets (Details) Note 6 - Fair Values of Assets and Liabilities - Reconciliation of Level 3 Assets (Details) Note 6 - Fair Values of Assets and Liabilities - Quantitative Information about Level 3 Assets and Liabilities Fair Value Measurements (Details) Note 6 - Fair Values of Assets and Liabilities - Summary of Fair Value Hierarchy for Liabilities (Details) Automobile Loan [Member] Note 6 - Fair Values of Assets and Liabilities - Reconciliation of Level 3 Liabilities (Details) Note 6 - Fair Values of Assets and Liabilities - Summary of Other Relevant Data (Details) Note 7 - Property - Schedule of Property (Details) Note 8 - Leases - Schedule of Minimum Lease Payments (Details) Note 9 - Notes Payable - Summary of Variable Interest Entities (Details) Share-based Compensation, Stock Options, Activity [Table Text Block] Note 9 - Notes Payable - Schedule of Structured Financing Notes Payable (Details) Note 9 - Notes Payable - Schedule of Structured Financing Notes Payable (Details) (Parentheticals) Note 9 - Notes Payable - Schedule of Notes Payable at Face Value and Notes Payable to Related Parties (Details) Note 9 - Notes Payable - Schedule of Notes Payable at Face Value and Notes Payable to Related Parties (Details) (Parentheticals) Note 10 - Convertible Senior Notes - Summary of Convertible Senior Notes (Details) Note 10 - Convertible Senior Notes - Summary of Convertible Senior Notes (Details) (Parentheticals) Note 12 - Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax Reclassifications of foreign currency translation adjustment to Other operating expense on the consolidated statements of operations Note 12 - Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) Note 12 - Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) Note 12 - Income Taxes - Unrecognized Tax Benefits Rollforward (Details) Note 13 - Net Loss Attributable to Controlling Interests Per Common Share - Summary of Earning Per Share (Details) Note 14 - Stock-based Compensation - Summary of Outstanding Options (Details) us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Notes To Financial Statements Number of accounts on non-accrual status Financing Receivable Modifications Number Of Contracts Outstanding. 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facility, maturity date Debt Instrument, Maturity Date Allowance for uncollectible loans, interest and fees receivable: New Accounting Pronouncements, Policy [Policy Text Block] us-gaap_SharesOutstanding Balance (in shares) Balance (in shares) Common stock, outstanding (in shares) Amortizing securitization facility, weighted average interest rate Debt, Weighted Average Interest Rate us-gaap_IncreaseDecreaseInOtherOperatingAssets Other Current Fiscal Year End Date us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 Debt Instrument, Basis Spread on Variable Rate Convertible senior notes, interest rate Debt Instrument, Interest Rate, Stated Percentage Document Fiscal Period Focus Document Fiscal Year Focus Document Period End Date us-gaap_IncreaseDecreaseInDepositsOutstanding Decrease in deposits Entity Emerging Growth Company Face amount of 5.875% convertible senior notes Amortizing securitization facility, outstanding face amount Debt Instrument, Face Amount Document Type 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Compensatory stock issuances, net of forfeitures (in shares) Stock option exercises and proceeds related thereto Chief Executive Officer [Member] Related Party [Axis] Related Party [Domain] atlc_PaymentsForIncomeTaxSettlementWithTaxingAuthority Payments for Income Tax Settlement with Taxing Authority The cash outflow for payments for income tax settlement with tax authority. Loans, interest and fees receivable: Issued (in shares) Revolving credit facility, expiration date Line of Credit Facility, Expiration Date Line of Credit Facility, Lender [Domain] Lender Name [Axis] us-gaap_LiabilitiesAndStockholdersEquity Total liabilities and deficit Retained deficit Accumulated other comprehensive income (loss) Measurement Input, Prepayment Rate [Member] Measurement Input, Discount Rate [Member] Debt Disclosure [Text Block] us-gaap_InterestExpense Interest expense Interest expense Measurement Input, Default Rate [Member] Changes in assets and liabilities: us-gaap_DisclosureTextBlockAbstract Notes to Financial Statements Subsequent Event [Member] us-gaap_OperatingLeaseLiability Operating Lease, Liability, Total Subsequent Event Type [Axis] Subsequent Event Type [Domain] us-gaap_OperatingLeaseRightOfUseAsset Operating Lease, Right-of-Use Asset Proceeds from equity-method investees us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardCompensationCost1 Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost, Total Measurement Input, Constant Prepayment Rate [Member] Measurement Input Type [Axis] Measurement Input Type [Domain] Valuation Technique, Discounted Cash Flow [Member] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Subsequent Events, Policy [Policy Text Block] us-gaap_ShareBasedCompensation Deferred stock-based compensation costs Interest expense from accretion of discount on notes Amortization of Debt Discount (Premium) us-gaap_OtherInterestAndDividendIncome Other us-gaap_InterestAndDividendIncomeOperating Total interest income Total interest income us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments Income from accretion of discount associated with receivables purchases us-gaap_LesseeOperatingLeaseTermOfContract Lessee, Operating Lease, Term of Contract us-gaap_Depreciation Depreciation, Total Depreciation, amortization and accretion, net Stockholders' Equity Note Disclosure [Text Block] Selling, General and Administrative Expenses, Policy [Policy Text Block] Advertising Cost, Policy, Expensed Advertising Cost [Policy Text Block] Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Common stock, no par value, 150,000,000 shares authorized: 15,563,574 shares issued and outstanding (including 1,459,233 loaned shares to be returned) at December 31, 2018; 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(2) fees associated with our credit card receivables; (3) changes in the fair value of loans and fees receivable; (4) changes in fair value of notes payable associated with structured financings; (5) income on investments in previously charged-off receivables; (6) gross profits and losses from auto sales; (7) gains associated with investments in securities; and (8) gains realized associated with our settlement of litigation. Members’ capital us-gaap_NetCashProvidedByUsedInOperatingActivities Net cash provided by (used in) operating activities us-gaap_DeferredTaxLiabilitiesOther Other Notes Payable, at fair value held by VIEs Notes payable associated with structured financings, at fair value Notes Payable Associated with Structured Financings, Fair Value Notes payable associated with structured financings, at fair value Debt that reflects the fair value of the consolidation of our securitization trusts presenting certain non-recourse, asset-backed structured financing debt facilities that are secured by these credit card receivables that are held within such trusts. us-gaap_NetCashProvidedByUsedInInvestingActivities Net cash used in investing activities Effect of exchange rate changes on cash Total liabilities Card and loan servicing Counterparty Name [Axis] (Net recovery of) losses upon impairment of loans, interest and fees receivable recorded at fair value Net recovery of (losses upon) impairment of loans, interest and fees receivable recorded at fair value Reflects charge offs associated with the de-securitization and reconsolidation of our lower-tier credit card receivables portfolio upon investor repayment and the consolidation of our formerly off-balance-sheet credit card receivables securitizations pursuant to accounting rules changes. Counterparty Name [Domain] us-gaap_DeferredTaxLiabilitiesDeferredExpense Deferred costs Loans, interest and fees receivables, at fair value Total assets us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssets atlc_UnrealizedGainOnLoansAndFeesReceivableAndUnderlyingNotesPayableHeldAtFairValue Unrealized gain on loans, interest and fees receivable and underlying notes payable held at fair value The aggregate increase (decrease) in the market value on loans and fees receivable and underlying notes payable held at fair value whose gains (losses) were included in earnings. Accounts Payable and Accrued Expenses [Policy Text Block] The entire policy related to accounts payable and accrued expenses. Prepaid Expenses and Other Assets [Policy Text Block] The entire policy related to prepaid expenses and other assets. us-gaap_DeferredTaxLiabilitiesFinancingArrangements Convertible senior notes atlc_WeightedAverageRemainingAccretionPeriodOfDeferredRevenue Weighted Average Remaining Accretion Period of Deferred Revenue Represents the weighted average remaining accretion period of deferred revenue during the reporting period. us-gaap_DeferredTaxLiabilitiesTaxDeferredIncome Cancellation of indebtedness income Accounting Standards Update 2016-02 [Member] us-gaap_InterestPayableCurrentAndNoncurrent Interest Payable Carrying value of receivables on non-accrual status (in thousands) Represents the carrying value of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings. Direct-to-Consumer [Member] Information related to items classified as direct-to-consumer. Point-of-Sale [Member] Information related to items classified as point-of-sale. us-gaap_DeferredTaxLiabilitiesInvestmentInNoncontrolledAffiliates Equity in income of equity-method investee Other Unsecured Lending Products [Member] Information related to other unsecured lending products. Accounts payable and accrued expenses Noncontrolling interests contributions, net Equity Method Investments [Policy Text Block] Components of Fees and Related Income on Earning Assets [Table Text Block] Tabular disclosure of the components of fees and related income on earning assets. Income tax liability us-gaap_DeferredTaxLiabilitiesZeroCouponNotes Market discount on loans Type of Adoption [Domain] Auto Finance [Member] Information related to auto finance. us-gaap_DeferredTaxLiabilitiesPrepaidExpenses Prepaid expenses and other Credit and Other Investments [Member] Information related to credit and other investments. Adjustments for New Accounting Pronouncements [Axis] Service Charges and Other Customer Related Fees [Member] Information related to service charges and other customer related fees. Servicing Income [Member] Information related to servicing income. Equity Method Investments and Joint Ventures Disclosure [Text Block] Equity Method Investments [Table Text Block] Depreciation of rental merchandise Represents the amount of depreciation of leased merchandise during the period. Noncontrolling Interest [Member] us-gaap_NoninterestExpense Total other operating expense Impact of foreign currency translation This element represents impact of foreign currency translation on assets measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period. Loans, interest and fees receivable, net for which it is practicable to estimate fair value This item represents a financial instrument (as defined) for which it is practicable to estimate fair value. This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents loan receivable as presented on the statement of financial position which may include mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts, or any other loans which are due the Company as of the balance sheet date. us-gaap_PaymentsForRepurchaseOfCommonStock Purchase and retirement of outstanding stock Measurement Input, Servicing Rate [Member] Measurement input represents the expected servicing rate. Measurement Input, Gross Yield [Member] Measurement input representing the gross yield. us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense Interest and penalties accrued Loans and fees receivable, measurement input Value of input used to measure loans and fees receivable. Five Point Eight Seven Five Percent Convertible Senior Notes Due Two Thousand Thirty Five [Member] Information related to 5.875% convertible senior notes due 2035. Retained Earnings [Member] Proceeds from exercise of stock options Aggregate unpaid principal balance within loans, interest and fees receivable that are reported at fair value This item represents the aggregate unpaid principal balance within loans and fees receivables that are reported at fair value for which the fair value option has been elected. Loans and Fees Receivable Pledged as Collateral, Fair Value [Member] Information related to loans and fees receivable pledged as collateral measured at fair value. us-gaap_CurrentStateAndLocalTaxExpenseBenefit Current tax (expense) benefit Loans and Fees Receivable at Fair Value [Member] Information related to loans and fees receivable measure at fair value. us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit Deferred tax (expense) benefit Changes in fair value of notes payable associated with structured financings recorded at fair value Net revaluations of notes payable associated with structured financings, at fair value This element represents [net] revaluations of notes payable liability measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period. us-gaap_StateAndLocalIncomeTaxExpenseBenefitContinuingOperations Total state and other income tax (expense) benefit Amortizing securitization facility, amount secured by credit card receivables and restricted cash Credit Card Receivables and Restricted Cash Carrying Amount as Security for Notes Payable This line item represents aggregate carrying amount of credit card receivables and restricted cash that provides security for structured financing notes, as of balance sheet date. Other operating expense: us-gaap_CurrentForeignTaxExpenseBenefit Current tax (expense) benefit, foreign Structured Financing Notes Payable [Member] Information related to notes payable associated with structured financing reported at fair value. us-gaap_DeferredForeignIncomeTaxExpenseBenefit Deferred tax benefit, foreign Aggregate fair value of notes payable This item represents the aggregate fair value of notes payable for which the fair value option has been elected. Additional Paid-in Capital [Member] us-gaap_ForeignIncomeTaxExpenseBenefitContinuingOperations Total federal income tax expense (benefit), foreign Common Stock [Member] us-gaap_CurrentFederalTaxExpenseBenefit Current tax benefit (expense) us-gaap_DeferredFederalIncomeTaxExpenseBenefit Deferred tax (expense) benefit us-gaap_FederalIncomeTaxExpenseBenefitContinuingOperations Total federal income tax expense (benefit), federal us-gaap_IncomeTaxExaminationLiabilityRefundAdjustmentFromSettlementWithTaxingAuthority Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority Equity Components [Axis] Equity Component [Domain] us-gaap_IncomeTaxExaminationPenaltiesAccrued Income Tax Examination, Penalties Accrued us-gaap_CapitalLeaseObligations Capital Lease Obligations, Total Class of Financing Receivable, Type [Domain] us-gaap_NotesPayable Total notes payable outstanding Class of Financing Receivable, Type [Axis] Notes Payable, at face value held by VIEs Notes payable, at face value Revolving credit facilities Long-term Line of Credit, Total Other comprehensive income (loss): Convertible senior notes Net carrying value us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet Unamortized debt issuance costs and discounts Amortizing debt facilities Disaggregation of Revenue [Table Text Block] us-gaap_RepaymentsOfLongTermDebt Repayment of borrowings The 2014 Plan [Member] Information related to the 2014 Equity Incentive Plan (the "2014 Plan"). Employee Stock Purchase Plan [Member] Information related to the Employee Stock Purchase Plan (the "ESPP"). Senior Secured Term Loan Facility [Member] Information related to a Senior Secured Term Loan Facility. Dove Ventures, LLC [Member] Information related to Dove Ventures, LLC, a Nevada limited liability company ("Dove"). Computer Equipment [Member] atlc_AggregateExposureToPretaxEquityLossStructuredFinancingAtFairValue Aggregate Exposure to Pretax Equity Loss, Structured Financing at Fair Value Represents the aggregate exposure to pre-tax equity loss associated with structured financing measured at fair value. Trust Funding Notes Facility [Member] Information related to a program where the company may sell certain receivables to a consolidated trust in exchange for notes issued by the trust by an unaffiliated third party. Cash and Cash Equivalents, Unrestricted Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] us-gaap_DebtInstrumentUnamortizedDiscount Discount Receivables, Policy [Policy Text Block] Revolving Credit Facility Expiring October 30, 2019 [Member] Information related to a revolving credit facility expiring October 30, 2019. Balance Balance us-gaap_UnrecognizedTaxBenefits us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Basis of Accounting, Policy [Policy Text Block] Additional Trust Funding Notes Facility [Member] Information related to an additional program where the company may sell certain receivables to a consolidated trust in exchange for notes issued by the trust by an unaffiliated third party. Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block] Revolving Credit Facility Expiring December 31, 2019 [Member] Information related to a revolving credit facility expiring December 31, 2019. Revolving Credit Facility Expiring December 21, 2019 [Member] Information related to a revolving credit facility expiring December 21, 2019. Revolving Credit Facility Expiring June 25, 2020 [Member] Information related t a revolving credit facility expiring June 25, 2020. Revolving Credit Facility Expiring June 11, 2020 [Member] Information related to a revolving credit facility expiring June 11, 2020. Revolving Credit Facility Expiring February 8, 2022 [Member] Information related to a revolving credit facility expiring February 8, 2022. us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions Additions based on tax positions related to the current year Reductions based on tax positions related to prior years Amount of securing assets This line item represents aggregate carrying amount of receivables and other assets that provides security for structured financing notes, as of balance sheet date. Amortizing Debt Facility Expiring November 30, 2018 [Member] Information related to an amortizing debt facility expiring November 30, 2018. Proceeds from borrowings Proceeds from Issuance of Long-term Debt, Total us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesExpense Unrecognized Tax Benefits, Income Tax Penalties Expense Total notes payable before unamortized debt issuance costs and discounts The gross amount of Notes Payable. Changes in fair value of loans, interest and fees receivable recorded at fair value Represents the increase (decrease) during the period in the fair value of loans and fees receivable. Unfunded Outstanding Floor-Plan Financing Commitment [Member] Information related to unfunded outstanding floor-plan financing commitments. Unfunded Individual Credit Commitment [Member] Information related to unfunded commitments related to consumers ability to borrow up to the maximum credit limit assigned to each individual account. Fees on credit products Represents the amount of revenue related to fees on credit products. Rental revenue Amount of leased merchandise revenue and associated fees during the period. Segments [Axis] Segments [Domain] us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding Diluted (including unvested share-based payment awards) (1) (in shares) Notes payable to related parties Notes Payable, Related Parties Non-US [Member] Asset Class [Axis] Asset Class [Domain] Statement [Table] Scenario [Axis] Statement of Financial Position [Abstract] Net income (loss) attributable to controlling interests per common share—diluted (in dollars per share) Scenario, Unspecified [Domain] Thereafter, gross Amortizing Debt Facility Repaid June 2018 [Member] Information related to an amortizing debt facility repaid in June 2018. Basic (including unvested share-based payment awards) (1) (in shares) us-gaap_OperatingLeasesFutureMinimumPaymentsDue Total, gross Amortizing Debt Facility Repaid March 2018 [Member] Information related to an amortizing debt facility repaid in March 2018. us-gaap_EffectiveIncomeTaxRateContinuingOperations Effective Income Tax Rate Reconciliation, Percent, Total Effective benefit rate 2022, gross Net income (loss) attributable to controlling interests per common share—basic (in dollars per share) Impact of change in federal tax rate 2023, gross Federal valuation allowance Amortizing Debt Facility Repaid September 2018 [Member] Information related to an amortizing debt facility repaid in September 2018. 2020, gross Statement of Cash Flows [Abstract] 2021, gross Statement of Stockholders' Equity [Abstract] atlc_InterestIncomeExpenseBeforeFees Net interest income before fees and related income on earning assets and provision for losses on loans, interest and fees receivable The net amount of operating interest income (expense) before fees. 2019, gross Income Statement [Abstract] Schedule of Credit Losses Related to Financing Receivables, Current and Noncurrent [Table Text Block] Interest and penalties related to uncertain tax positions and IRS settlement adjustment Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Permanent and other prior year true ups and tax effect of non-controlling interest Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Provision for losses on loans, interest and fees receivable Provision for loan losses Provision for losses on loans, interest and fees receivable recorded at net realizable value Amount of expense for provision for losses on loans and fees receivable recorded at net realizable value. us-gaap_OtherCommitment Other Commitment, Total State taxes, net of valuation allowance Foreign taxes, net of valuation allowance Other Commitments [Axis] Fair Value, Assets Measured on Recurring Basis [Table Text Block] Other Commitments [Domain] Fair Value, Liabilities Measured on Recurring Basis [Table Text Block] Financing activities Statutory benefit rate Convertible senior notes us-gaap_ConvertibleDebtFairValueDisclosures Foreign currency translation adjustment us-gaap_StockholdersEquity Total shareholders’ deficit Class of Stock [Axis] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]