Loans Receivable (Schedule of Loans Receivable) (Details) - USD ($) $ in Millions		Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	[1],[2]	$ 9,599.6		$ 9,165.5
Allowance for credit losses		(2,989.3)		(2,867.8)
Loans receivable, net		6,610.3	$ 6,500.3	6,297.7	$ 6,323.7	$ 6,327.2	$ 6,336.3
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	[1]	6,534.1		6,074.8
Allowance for credit losses		(2,188.4)		(2,000.0)
Loans receivable, net		4,345.7	4,241.2	4,074.8	3,988.1	3,920.6	3,887.3
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	[2]	3,065.5		3,090.7
Allowance for credit losses		(800.9)		(867.8)
Loans receivable, net		$ 2,264.6	$ 2,259.1	$ 2,222.9	$ 2,335.6	$ 2,406.6	$ 2,449.0

[1] As Consumer Loans are aggregated by Dealer for purposes of recognizing revenue and measuring credit losses, the Dealer Loan amount was estimated by allocating the balance of each Dealer Loan to the underlying Consumer Loans based on the forecasted future collections of each Consumer Loan.

[2] As certain Consumer Loans are aggregated by Dealer or month of purchase for purposes of recognizing revenue and measuring credit losses, the Purchased Loan amount was estimated by allocating the balance of certain Purchased Loans to the underlying Consumer Loans based on the forecasted future collections of each Consumer Loan.