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Summary Of Significant Accounting Policies (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2016 USD ($) portfolio_segment | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Number of Portfolio Segments | portfolio_segment |  | 2 |  |  |
Number of Reportable Segments | portfolio_segment |  | 1 |  |  |
Monthly fee charged Dealer in Portfolio Program |  | $ 599 |  |  |
One-time enrollment fee in program |  | $ 9,850 |  |  |
Percentage of first accelerated Dealer Holdback payment retained |  | 50.00% |  |  |
Percentage of enrollment fee of first accelerated dealer holdback payment |  | 50.00% |  |  |
Period after Consumer Loan assignment that Dealer Loans written off |  | 120 months |  |  |
Period after month of purchase that Purchased Loans written off |  | 120 months |  |  |
Unamortized Debt Issuance Costs |  | $ 16,800,000 | $ 16,800,000 |  |
Threshold to determine likelihood of being sustained |  | 50.00% |  |  |
Employer matching contribution, match percentage |  | 100.00% |  |  |
Matching contribution |  | 1.00% |  |  |
Employer matching contribution, additional match percentage |  | 50.00% |  |  |
Additional matching contribution |  | 5.00% |  |  |
Maximum matching contribution |  | 3.50% |  |  |
Recognized compensation expense |  | $ 3,600,000 | 3,100,000 |  | $ 2,500,000
Advertising expense |  | 300,000 | 300,000 |  | $ 300,000
Cash and Cash Equivalents [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Uninsured cash and cash equivalents |  | 14,300,000 | 6,000,000 |  |
Restricted Cash And Cash Equivalents [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Uninsured cash and cash equivalents |  | $ 224,100,000 | 165,100,000 |  |
Building [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Estimated useful lives |  | P40Y |  |  |
Building Improvements [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Estimated useful lives |  | P10Y |  |  |
Data Processing Equipment [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Estimated useful lives |  | P3Y |  |  |
Software [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Estimated useful lives |  | P5Y |  |  |
Office Furniture And Equipment [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Estimated useful lives |  | P7Y |  |  |
Leasehold Improvements [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Estimated useful lives |  | P7Y |  |  |
Software Development [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Estimated useful lives |  | P5Y |  |  |
Secured financings [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Unamortized Debt Issuance Costs | [1] | $ 9,700,000 | 8,500,000 | [2] |
Senior Notes [Member] |  |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |
Unamortized Debt Issuance Costs |  | $ 7,100,000 | $ 8,300,000 | [2] |
[1] | Warehouse facilities and Term ABS financings.
[2] | Prior year amounts have been reclassified to reflect the adoption of ASU 2015-03, as amended by ASU No. 2015-15, which resulted in a reclassification of certain deferred debt issuance costs from other assets to secured financing and senior notes.

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