Loans Receivable (Write-Offs Segmented by Year of Assignment) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year, Writeoff	$ 53.8		$ 178.8
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	69.4		219.2
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	52.7		158.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	59.0		166.6
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	70.2		196.9
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	28.8		43.5
Allowance for Loan and Lease Losses, Write-offs	0.0	$ 0.0	0.0	$ 0.0
Allowance for Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Allowance for Loan and Lease Losses, Write-offs	333.9	348.8	963.9	1,017.6
Dealer Loans [Member]
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year, Writeoff	29.5		95.1
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	26.2		76.9
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	28.9		80.2
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	30.3		75.7
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	31.7		78.0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	7.1		11.3
Allowance for Loan and Lease Losses, Write-offs	0.0	0.0	0.0	0.0
Dealer Loans [Member] | Allowance for Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Allowance for Loan and Lease Losses, Write-offs	153.7	116.1	417.2	315.8
Purchased Loans [Member]
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year, Writeoff	24.3		83.7
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	43.2		142.3
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	23.8		78.7
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	28.7		90.9
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	38.5		118.9
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	21.7		32.2
Allowance for Loan and Lease Losses, Write-offs	0.0	0.0	0.0	0.0
Purchased Loans [Member] | Allowance for Credit Losses [Member]
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Allowance for Loan and Lease Losses, Write-offs	$ 180.2	$ 232.7	$ 546.7	$ 701.8