Loans Receivable Loans Receivable (Summary of Provision for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	$ 250.5	$ 147.5	$ 387.9	$ 170.8
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	144.6	73.3	219.3	74.8
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	105.9	74.2	168.6	96.0
New Consumer Loan Assignments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	81.7	97.5	174.8	200.1
New Consumer Loan Assignments [Member] | Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	33.8	45.6	71.5	93.1
New Consumer Loan Assignments [Member] | Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	47.9	51.9	103.3	107.0
Forecast Changes [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	168.8	50.0	213.1	(29.3)
Forecast Changes [Member] | Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	110.8	27.7	147.8	(18.3)
Forecast Changes [Member] | Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	$ 58.0	$ 22.3	$ 65.3	$ (11.0)