Loans Receivable (Write-Offs Segmented by Year of Assignment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year, Writeoff	$ 86.7	$ 63.1
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	47.1	72.0
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	56.8	52.5
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	73.3	51.7
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	44.9	59.3
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	2.6	2.0
Allowance for Loan and Lease Losses, Write-offs	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	311.4	300.6
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	45.2	31.6
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	25.3	23.7
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	28.9	23.7
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	33.2	18.8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	9.0	19.0
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	1.2	0.9
Allowance for Loan and Lease Losses, Write-offs	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	142.8	117.7
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	41.5	31.5
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff	21.8	48.3
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff	27.9	28.8
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff	40.1	32.9
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff	35.9	40.3
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Writeoff	1.4	1.1
Allowance for Loan and Lease Losses, Write-offs	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	$ 168.6	$ 182.9