Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation: The consolidated financial statements of the Company have been prepared in accordance with the instructions to the Quarterly Report on Form 10-Q adopted by the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and, accordingly, do not include all information and note disclosures required by GAAP for complete financial statements. The interim financial statements in this Quarterly Report on Form 10-Q have not been audited by an independent registered public accounting firm in accordance with standards of the Public Company Accounting Oversight Board (United States), but in the opinion of management, the interim financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the Company’s financial position, results of operations, and cash flows in accordance with GAAP. These consolidated financial statements should be read in conjunction with the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, as filed with the SEC.
Significant accounting policies	Significant accounting policies: The following is a description of significant accounting policies used in preparing the financial statements. The accounting and reporting policies of the Company are in accordance with GAAP and conform to general practices within the consumer finance industry.
Principles of consolidation	*Principles of consolidation:* The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. The Company operates through a separate wholly-owned subsidiary in each state. The Company also consolidates variable interest entities (each, a “VIE”) when it is considered to be the primary beneficiary of the VIE because it has (i) power over the significant activities of the VIE and (ii) the obligation to absorb losses or the right to receive returns that could be significant to the VIE.
Variable interest entities	*Variable interest entities:* The Company transfers pools of loans to wholly-owned, bankruptcy-remote, special purpose entities (each, an “SPE”) to secure debt for general funding purposes. These entities have the limited purpose of acquiring finance receivables and holding and making payments on the related debts. Assets transferred to each SPE are legally isolated from the Company and its affiliates, as well as the claims of the Company’s and its affiliates’ creditors. Further, the assets of each SPE are owned by such SPE and are not available to satisfy the debts or other obligations of the Company or any of its affiliates. The Company continues to service the finance receivables transferred to the SPEs. The lenders and investors in the debt issued by the SPEs generally only have recourse to the assets of the SPEs and do not have recourse to the general credit of the Company. The SPEs’ debt arrangements are structured to provide enhancements to the lenders and investors in the form of overcollateralization (the principal balance of the collateral exceeds the balance of the debt) and reserve funds (restricted cash held by the SPEs). These enhancements, along with the isolated finance receivables pools, increase the creditworthiness of the SPEs above that of the Company as a whole. This increases the marketability of the Company’s collateral for borrowing purposes, leading to more favorable borrowing terms, improved interest rate risk management, and additional flexibility to grow the business. The SPEs are considered VIEs under GAAP and are consolidated into the financial statements of their primary beneficiary. The Company is considered to be the primary beneficiary of the SPEs because it has (i) power over the significant activities through its role as servicer of the finance receivables under each debt arrangement and (ii) the obligation to absorb losses or the right to receive returns that could be significant through the Company’s interest in the monthly residual cash flows of the SPEs after each debt is paid. Consolidation of VIEs results in these transactions being accounted for as secured borrowings; therefore, the pooled receivables and the related debts remain on the consolidated balance sheet of the Company. Each debt is secured solely by the assets of the VIEs and not by any other assets of the Company. The assets of the VIEs are the only source of funds for repayment on each debt, and restricted cash held by the VIEs can only be used to support payments on the debt. The Company recognizes revenue and provision for credit losses on the finance receivables of the VIEs and interest expense on the related secured debt.
Use of estimates	*Use of estimates:* The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenues and expenses, and disclosure of contingent assets and liabilities for the periods indicated in the financial statements. Actual results could differ from those estimates. Material estimates that are particularly susceptible to change relate to the determination of the allowance for credit losses, the fair value of share-based compensation, the valuation of deferred tax assets and liabilities, contingent liabilities on litigation matters, and the allocation of the purchase price to assets acquired in business combinations.
Reclassifications	*Reclassifications:* Certain prior-period amounts have been reclassified to conform to the current presentation. Such reclassifications had no impact on previously reported net income or stockholders’ equity.
Recent accounting pronouncements	*Recent accounting pronouncements:* In February 2016, the Financial Accounting Standards Board (“FASB”) issued an accounting update to increase transparency and comparability of accounting for lease transactions. The update required: (i) all leases to be recognized on the balance sheet as lease (right-of-use) assets and lease liabilities and (ii) both quantitative and qualitative disclosures regarding key information about leasing arrangements. The update was effective for annual and interim periods beginning after December 15, 2018. The Company completed the implementation of third-party software to facilitate compliance with the accounting and reporting requirements of the lease standard. Prior to adoption, all of the Company’s leases were classified as operating leases, with no lease assets or liabilities recorded. The Company transitioned to this accounting change on a modified retrospective basis by recording the cumulative-effect of lease assets and liabilities for active leases as of January 1, 2019. The Company did not restate comparative periods in transition and elected to use the effective date of January 1, 2019 as the initial date of transition. The Company also elected to utilize the package of transition practical expedients, which included not reassessing the following: (i) whether existing contracts contain leases, (ii) the existing classification of leases as operating or financing, or (iii) the initial direct costs of leases. The Company did not use hindsight to determine the lease term or include options to extend for leases existing at the transition date. In addition, the Company elected not to apply the new lease standard to leases with terms of twelve months or less. As a result of the adoption of the new lease standard on January 1, 2019, the Company recorded $24.1 million for both lease liabilities and the corresponding lease assets. The lease liabilities were based on the present value of the remaining minimum rental payments using discount rates as of the effective date. There was no impact to the consolidated statements of income related to the adoption of this standard. The adoption of this standard did not require the Company to alter its debt covenants. In June 2016, the FASB issued an accounting update to change the impairment model for estimating credit losses on financial assets. The current incurred loss impairment model requires the recognition of credit losses when it is probable that a loss has been incurred. The incurred loss model will be replaced by an expected loss model, which requires entities to estimate the lifetime expected credit loss on such instruments and to record an allowance to offset the amortized cost basis of the financial asset. This update is effective for annual and interim periods beginning after December 15, 2019, and early adoption is permitted. The Company believes the implementation of the accounting update will have a material adverse effect on the Company’s consolidated financial statements and is in the process of quantifying the potential impacts. In August 2018, the FASB issued an accounting update to provide additional guidance on the accounting for costs of implementation activities performed in a cloud computing arrangement that is a service contract. The amendments align the capitalization requirements for hosting arrangements that are service contracts with the capitalization principles for internal-use software. This update is effective for annual and interim periods beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the potential impact of this update on its consolidated financial statements.