Loans Receivable Loans Receivable (Summary of Past-Due Status) - USD ($) $ in Millions	Jun. 30, 2021		Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Loans receivable	$ 9,966.5	[1],[2]	$ 10,124.8
Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	6,699.3	[1],[2],[3],[4]	6,349.2
Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,539.9	[1],[2],[3]	1,936.3
Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,574.6	[1],[2],[3]	1,690.4
Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	152.7	[1],[2],[5]	148.9
Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	5,869.3	[1]	5,869.6
Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	4,071.3	[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	878.4	[1],[3]	1,090.1
Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	807.9	[1],[3]	882.3
Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	111.7	[1],[5]	113.0
Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	4,097.2	[2]	4,255.2
Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2,628.0	[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	661.5	[2],[3]	846.2
Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	766.7	[2],[3]	808.1
Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	41.0	[2],[5]	35.9
Loans Originating In The Current Year
Financing Receivable, Past Due [Line Items]
Loans receivable	2,062.9	[1],[2]	3,818.6
Loans Originating In The Current Year | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,850.4	[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	206.7	[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	5.8	[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	1,422.2	[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	1,276.5	[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	141.8	[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	3.9	[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	640.7	[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	573.9	[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	64.9	[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	1.9	[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	3,126.8	[1],[2]	3,341.6
Loans Originating In The Prior Year | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2,306.9	[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	554.7	[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	265.1	[1],[2],[3]	610.8
Loans Originating In The Prior Year | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.1	[1],[2],[5]	0.0
Loans Originating In The Prior Year | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2,036.1	[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	1,512.3	[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	355.0	[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	168.7	[1],[3]	310.2
Loans Originating In The Prior Year | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.1	[1],[5]	0.0
Loans Originating In The Prior Year | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,090.7	[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	794.6	[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	199.7	[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	96.4	[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	2,656.2	[1],[2]	1,852.3
Loans Originating Two Years Prior | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,595.2	[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	486.0	[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	574.8	[1],[2],[3]	513.9
Loans Originating Two Years Prior | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.2	[1],[2],[5]	1.0
Loans Originating Two Years Prior | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1,314.4	[1]	988.9
Loans Originating Two Years Prior | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	800.1	[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	235.2	[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	279.0	[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	1,341.8	[2]	863.4
Loans Originating Two Years Prior | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	795.1	[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	250.8	[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	295.8	[2],[3]	246.5
Loans Originating Two Years Prior | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	0.1	[2],[5]	0.3
Loans Originating Three Years Prior
Financing Receivable, Past Due [Line Items]
Loans receivable	1,381.8	[1],[2]	726.6
Loans Originating Three Years Prior | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	720.9	[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	222.3	[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	435.3	[1],[2],[3]	277.5
Loans Originating Three Years Prior | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	3.3	[1],[2],[5]	7.2
Loans Originating Three Years Prior | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	706.7	[1]	381.6
Loans Originating Three Years Prior | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	373.6	[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	112.7	[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	218.2	[1],[3]	143.3
Loans Originating Three Years Prior | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	2.2	[1],[5]	5.1
Loans Originating Three Years Prior | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	675.1	[2]	345.0
Loans Originating Three Years Prior | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	347.3	[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	109.6	[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	217.1	[2],[3]	134.2
Loans Originating Three Years Prior | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	1.1	[2],[5]	2.1
Loans Originating Four Years Prior
Financing Receivable, Past Due [Line Items]
Loans receivable	486.3	[1],[2]	263.6
Loans Originating Four Years Prior | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	194.3	[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	59.5	[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	215.7	[1],[2],[3]	119.3
Loans Originating Four Years Prior | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	16.8	[1],[2],[5]	41.7
Loans Originating Four Years Prior | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	245.3	[1]	131.0
Loans Originating Four Years Prior | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	96.9	[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	29.7	[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	107.2	[1],[3]	55.7
Loans Originating Four Years Prior | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	11.5	[1],[5]	31.1
Loans Originating Four Years Prior | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	241.0	[2]	132.6
Loans Originating Four Years Prior | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	97.4	[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	29.8	[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	108.5	[2],[3]	63.6
Loans Originating Four Years Prior | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	5.3	[2],[5]	10.6
Loans Originating Five Years Prior And Before
Financing Receivable, Past Due [Line Items]
Loans receivable	252.5	[1],[2]	122.1
Loans Originating Five Years Prior And Before | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	31.6	[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	10.7	[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	77.9	[1],[2],[3]	16.1
Loans Originating Five Years Prior And Before | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	132.3	[1],[2],[5]	99.0
Loans Originating Five Years Prior And Before | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	144.6	[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	11.9	[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	4.0	[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	30.9	[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	97.8	[1],[5]	76.1
Loans Originating Five Years Prior And Before | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	107.9	[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	19.7	[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	6.7	[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	47.0	[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	$ 34.5	[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.