Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($) segment portfolio_segment	Dec. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Document Period End Date	Jun. 30, 2019
Number of reportable segments | segment	1
Uninsured cash and cash equivalents	$ 19.4	$ 25.1
Number of portfolio segments | portfolio_segment	2
Period after Consumer Loan assignment that Dealer Loans written off	120 months
Period after month of purchase that Purchased Loans written off	120 months
Right-of-use asset	$ 3.3
Lease liability	3.5
Restricted Cash and Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents	$ 325.5	$ 303.0