Loans Receivable (Write-Offs Segmented by Year of Assignment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 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	$ 61.9		$ 125.0
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	77.9		149.9
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	53.7		106.2
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	55.8		107.6
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	67.4		126.7
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	12.7		14.6
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	329.4	326.0	630.0	668.8
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	33.9		65.5
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	27.1		50.8
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	27.6		51.3
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	26.6		45.4
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	27.3		46.3
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	3.3		4.2
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	145.8	100.9	263.5	199.7
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	28.0		59.5
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	50.8		99.1
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	26.1		54.9
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	29.2		62.2
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	40.1		80.4
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	9.4		10.4
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	$ 183.6	$ 225.1	$ 366.5	$ 469.1