Finance Receivables, net (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Face value of receivable portfolios	$ 1,800.0	$ 2,200.0	$ 6,600.0	$ 3,700.0
Payments to acquire finance receivables	289.2	221.4	608.0	389.7
Estimated remaining collections on purchased receivables	513.0	$ 311.3	1,020.0	$ 523.2
Unamortized purchased principal (purchase price) under the cost recovery method	$ 39.4		$ 39.4		$ 48.0