Loans Receivable Loans Receivable (Summary of Past-Due Status) - USD ($) $ in Millions	Mar. 31, 2021		Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Loans receivable	$ 10,158.0	[1],[2]	$ 10,124.8
Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	7,034.6	[1],[2],[3],[4]	6,349.2
Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,365.1	[1],[2],[3]	1,936.3
Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,608.5	[1],[2],[3]	1,690.4
Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	149.8	[1],[2],[5]	148.9
Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	5,933.5	[1]	5,869.6
Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	4,225.4	[1],[3],[4]	3,784.2
Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	766.3	[1],[3]	1,090.1
Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	830.4	[1],[3]	882.3
Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	111.4	[1],[5]	113.0
Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	4,224.5	[2]	4,255.2
Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2,809.2	[2],[3],[4]	2,565.0
Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	598.8	[2],[3]	846.2
Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	778.1	[2],[3]	808.1
Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	38.4	[2],[5]	35.9
Loans Originating In The Current Year
Financing Receivable, Past Due [Line Items]
Loans receivable	1,223.8	[1],[2]	3,818.6
Loans Originating In The Current Year | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,187.2	[1],[2],[3],[4]	3,002.0
Loans Originating In The Current Year | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	36.6	[1],[2],[3]	663.8
Loans Originating In The Current Year | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[1],[2],[3]	152.8
Loans Originating In The Current Year | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[1],[2],[5]	0.0
Loans Originating In The Current Year | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	843.1	[1]	2,540.4
Loans Originating In The Current Year | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	817.6	[1],[3],[4]	2,009.5
Loans Originating In The Current Year | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	25.5	[1],[3]	433.1
Loans Originating In The Current Year | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[1],[3]	97.8
Loans Originating In The Current Year | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[1],[5]	0.0
Loans Originating In The Current Year | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	380.7	[2]	1,278.2
Loans Originating In The Current Year | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	369.6	[2],[3],[4]	992.5
Loans Originating In The Current Year | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	11.1	[2],[3]	230.7
Loans Originating In The Current Year | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[2],[3]	55.0
Loans Originating In The Current Year | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[2],[5]	0.0
Loans Originating In The Prior Year
Financing Receivable, Past Due [Line Items]
Loans receivable	3,456.4	[1],[2]	3,341.6
Loans Originating In The Prior Year | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2,754.7	[1],[2],[3],[4]	1,985.2
Loans Originating In The Prior Year | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	492.1	[1],[2],[3]	745.6
Loans Originating In The Prior Year | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	209.6	[1],[2],[3]	610.8
Loans Originating In The Prior Year | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[1],[2],[5]	0.0
Loans Originating In The Prior Year | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2,277.6	[1]	1,740.6
Loans Originating In The Prior Year | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,822.0	[1],[3],[4]	1,046.9
Loans Originating In The Prior Year | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	320.8	[1],[3]	383.5
Loans Originating In The Prior Year | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	134.8	[1],[3]	310.2
Loans Originating In The Prior Year | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[1],[5]	0.0
Loans Originating In The Prior Year | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,178.8	[2]	1,601.0
Loans Originating In The Prior Year | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	932.7	[2],[3],[4]	938.3
Loans Originating In The Prior Year | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	171.3	[2],[3]	362.1
Loans Originating In The Prior Year | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	74.8	[2],[3]	300.6
Loans Originating In The Prior Year | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[2],[5]	0.0
Loans Originating Two Years Prior
Financing Receivable, Past Due [Line Items]
Loans receivable	2,982.8	[1],[2]	1,852.3
Loans Originating Two Years Prior | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,898.1	[1],[2],[3],[4]	962.8
Loans Originating Two Years Prior | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	498.4	[1],[2],[3]	374.6
Loans Originating Two Years Prior | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	586.2	[1],[2],[3]	513.9
Loans Originating Two Years Prior | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.1	[1],[2],[5]	1.0
Loans Originating Two Years Prior | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,506.0	[1]	988.9
Loans Originating Two Years Prior | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	966.6	[1],[3],[4]	523.3
Loans Originating Two Years Prior | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	249.4	[1],[3]	197.5
Loans Originating Two Years Prior | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	289.9	[1],[3]	267.4
Loans Originating Two Years Prior | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.1	[1],[5]	0.7
Loans Originating Two Years Prior | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,476.8	[2]	863.4
Loans Originating Two Years Prior | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	931.5	[2],[3],[4]	439.5
Loans Originating Two Years Prior | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	249.0	[2],[3]	177.1
Loans Originating Two Years Prior | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	296.3	[2],[3]	246.5
Loans Originating Two Years Prior | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.0	[2],[5]	0.3
Loans Originating Three Years Prior
Financing Receivable, Past Due [Line Items]
Loans receivable	1,593.7	[1],[2]	726.6
Loans Originating Three Years Prior | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	879.8	[1],[2],[3],[4]	320.9
Loans Originating Three Years Prior | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	246.5	[1],[2],[3]	121.0
Loans Originating Three Years Prior | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	465.4	[1],[2],[3]	277.5
Loans Originating Three Years Prior | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2.0	[1],[2],[5]	7.2
Loans Originating Three Years Prior | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	829.0	[1]	381.6
Loans Originating Three Years Prior | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	464.3	[1],[3],[4]	170.5
Loans Originating Three Years Prior | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	126.0	[1],[3]	62.7
Loans Originating Three Years Prior | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	237.4	[1],[3]	143.3
Loans Originating Three Years Prior | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1.3	[1],[5]	5.1
Loans Originating Three Years Prior | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	764.7	[2]	345.0
Loans Originating Three Years Prior | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	415.5	[2],[3],[4]	150.4
Loans Originating Three Years Prior | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	120.5	[2],[3]	58.3
Loans Originating Three Years Prior | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	228.0	[2],[3]	134.2
Loans Originating Three Years Prior | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.7	[2],[5]	2.1
Loans Originating Four Years Prior
Financing Receivable, Past Due [Line Items]
Loans receivable	592.1	[1],[2]	263.6
Loans Originating Four Years Prior | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	261.9	[1],[2],[3],[4]	73.5
Loans Originating Four Years Prior | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	75.1	[1],[2],[3]	29.1
Loans Originating Four Years Prior | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	243.7	[1],[2],[3]	119.3
Loans Originating Four Years Prior | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	11.4	[1],[2],[5]	41.7
Loans Originating Four Years Prior | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	303.3	[1]	131.0
Loans Originating Four Years Prior | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	133.8	[1],[3],[4]	31.9
Loans Originating Four Years Prior | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	37.9	[1],[3]	12.3
Loans Originating Four Years Prior | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	123.6	[1],[3]	55.7
Loans Originating Four Years Prior | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	8.0	[1],[5]	31.1
Loans Originating Four Years Prior | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	288.8	[2]	132.6
Loans Originating Four Years Prior | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	128.1	[2],[3],[4]	41.6
Loans Originating Four Years Prior | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	37.2	[2],[3]	16.8
Loans Originating Four Years Prior | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	120.1	[2],[3]	63.6
Loans Originating Four Years Prior | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	3.4	[2],[5]	10.6
Loans Originating Five Years Prior And Before
Financing Receivable, Past Due [Line Items]
Loans receivable	309.2	[1],[2]	122.1
Loans Originating Five Years Prior And Before | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	52.9	[1],[2],[3],[4]	4.8
Loans Originating Five Years Prior And Before | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	16.4	[1],[2],[3]	2.2
Loans Originating Five Years Prior And Before | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	103.6	[1],[2],[3]	16.1
Loans Originating Five Years Prior And Before | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	136.3	[1],[2],[5]	99.0
Loans Originating Five Years Prior And Before | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	174.5	[1]	87.1
Loans Originating Five Years Prior And Before | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	21.1	[1],[3],[4]	2.1
Loans Originating Five Years Prior And Before | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	6.7	[1],[3]	1.0
Loans Originating Five Years Prior And Before | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	44.7	[1],[3]	7.9
Loans Originating Five Years Prior And Before | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	102.0	[1],[5]	76.1
Loans Originating Five Years Prior And Before | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	134.7	[2]	35.0
Loans Originating Five Years Prior And Before | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	31.8	[2],[3],[4]	2.7
Loans Originating Five Years Prior And Before | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	9.7	[2],[3]	1.2
Loans Originating Five Years Prior And Before | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	58.9	[2],[3]	8.2
Loans Originating Five Years Prior And Before | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	$ 34.3	[2],[5]	$ 22.9

[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.

[3] Represents the Loan balance attributable to Consumer Loans outstanding within their initial loan terms.

[4] We consider a Consumer Loan to be current for purposes of forecasting expected collection rates if contractual repayments are less than 11 days past due.

[5] Represents the Loan balance attributable to Consumer Loans outstanding beyond their initial loan terms.