Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) portfolio_segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 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
Period after Consumer Loan assignment that Dealer Loans written off	120 months
Period after month of purchase that Purchased Loans written off	120 months
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	$ 7,100,000	$ 5,300,000	$ 4,600,000
Advertising expense	300,000	200,000	$ 400,000
Cash and Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents	186,100,000	25,100,000
Restricted Cash And Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents	$ 326,700,000	$ 303,000,000.0
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