Loans Receivable (Summary of Provision for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	$ 736.2	$ 481.4	$ 8.4
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	427.7	240.4	(28.2)
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	308.5	241.0	36.6
New Consumer Loan assignments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	322.5	343.7	365.1
New Consumer Loan assignments | Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	146.2	154.8	153.1
New Consumer Loan assignments | Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	176.3	188.9	212.0
Forecast Changes [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	413.7	137.7	(356.7)
Forecast Changes [Member] | Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	281.5	85.6	(181.3)
Forecast Changes [Member] | Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for credit losses	$ 132.2	$ 52.1	$ (175.4)