Loans Receivable Loans Receivable (Summary of Provision for Credit Losses) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	$ 180.3	$ (8.3)	$ 351.1	$ (17.5)
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	95.2	(9.5)	170.0	(36.8)
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	85.1	1.2	181.1	19.3
New Consumer Loan Assignments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	83.4	75.5	283.5	298.9
New Consumer Loan Assignments [Member] | Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	37.6	32.0	130.7	123.2
New Consumer Loan Assignments [Member] | Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	45.8	43.5	152.8	175.7
Forecast Changes [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	96.9	(83.8)	67.6	(316.4)
Forecast Changes [Member] | Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	57.6	(41.5)	39.3	(160.0)
Forecast Changes [Member] | Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	$ 39.3	$ (42.3)	$ 28.3	$ (156.4)