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Summary Of Significant Accounting Policies (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2020 USD ($) portfolio_segment | Dec. 31, 2019 USD ($) | Dec. 31, 2018 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 |  |
Threshold to determine likelihood of being sustained |  | 50.00% |  |
Employer matching contribution, match percentage |  | 100.00% |  |
Matching contribution |  | 4.00% |  |
Employer matching contribution, additional match percentage |  | 50.00% |  |
Additional matching contribution |  | 2.00% |  |
Maximum matching contribution |  | 5.00% |  |
Recognized compensation expense |  | $ 7,200,000 | $ 7,100,000 | $ 5,300,000
Advertising expense |  | 100,000 | 300,000 | $ 200,000
Adoption of CECL | [1] | 0 |  |
Cash and Cash Equivalents [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Uninsured cash and cash equivalents |  | 15,700,000 | 186,100,000 |
Restricted Cash And Cash Equivalents [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Uninsured cash and cash equivalents |  | $ 376,900,000 | $ 326,700,000 |
Building [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Estimated useful lives |  | 40 years |  |
Building Improvements [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Estimated useful lives |  | 10 years |  |
Data Processing Equipment [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Estimated useful lives |  | 3 years |  |
Software [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Estimated useful lives |  | 5 years |  |
Office Furniture And Equipment [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Estimated useful lives |  | 7 years |  |
Leasehold Improvements [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Estimated useful lives |  | 7 years |  |
Software Development [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Estimated useful lives |  | five years |  |
Annual Incremental Provision for Credit Losses on New Loans [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Adoption of CECL |  | $ 518,600,000 |  |
Annual Net Income Impact [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Adoption of CECL |  | 399,300,000 |  |
Annual Net Income Per Share Impact [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Adoption of CECL |  | 22.26 |  |
Loans Receivable and related Allowance for Credit Losses [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Adoption of CECL |  | 2,463,600,000 |  |
Allowance for Credit Losses [Member] |  |  |  |
Summary Of Significant Accounting Policies [Line Items] |  |  |  |
Adoption of CECL | [1] | $ 2,463,600,000 |  |
[1] | Represents the gross-up of Loans receivable and allowance for credit losses on January 1, 2020 upon the adoption of CECL for the present value of the difference between contractual future net cash flows and expected future net cash flows discounted at the effective interest rate.

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