Loans Receivable Loans Receivable (Summary of Past-Due Status) (Details) - USD ($) $ in Millions		Mar. 31, 2020		Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Loans receivable		$ 9,859.0	[1],[2]	$ 7,221.2
Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3],[4]	6,336.4
Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	1,933.9
Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	1,437.5
Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[5]	151.2
Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable		5,677.7	[1]	4,623.3
Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3],[4]	3,708.2
Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	1,073.6
Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	777.4
Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[5]	118.5
Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable		4,181.3	[2]	$ 2,597.9
Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3],[4]	2,628.2
Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	860.3
Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	660.1
Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[5]	32.7
Loans Originating In 2015 and Prior [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2]	217.3
Loans Originating In 2015 and Prior [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3],[4]	27.5
Loans Originating In 2015 and Prior [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	11.2
Loans Originating In 2015 and Prior [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	47.6
Loans Originating In 2015 and Prior [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[5]	131.0
Loans Originating In 2015 and Prior [Member] | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1]	153.5
Loans Originating In 2015 and Prior [Member] | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3],[4]	15.1
Loans Originating In 2015 and Prior [Member] | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	6.0
Loans Originating In 2015 and Prior [Member] | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	28.9
Loans Originating In 2015 and Prior [Member] | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[5]	103.5
Loans Originating In 2015 and Prior [Member] | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2]	63.8
Loans Originating In 2015 and Prior [Member] | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3],[4]	12.4
Loans Originating In 2015 and Prior [Member] | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	5.2
Loans Originating In 2015 and Prior [Member] | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	18.7
Loans Originating In 2015 and Prior [Member] | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[5]	27.5
Loans Originating In 2016 [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2]	474.4
Loans Originating In 2016 [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3],[4]	183.3
Loans Originating In 2016 [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	74.8
Loans Originating In 2016 [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	198.2
Loans Originating In 2016 [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[5]	18.1
Loans Originating In 2016 [Member] | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1]	253.9
Loans Originating In 2016 [Member] | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3],[4]	95.3
Loans Originating In 2016 [Member] | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	37.6
Loans Originating In 2016 [Member] | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	107.5
Loans Originating In 2016 [Member] | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[5]	13.5
Loans Originating In 2016 [Member] | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2]	220.5
Loans Originating In 2016 [Member] | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3],[4]	88.0
Loans Originating In 2016 [Member] | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	37.2
Loans Originating In 2016 [Member] | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	90.7
Loans Originating In 2016 [Member] | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[5]	4.6
Loans Originating In 2017 [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2]	1,131.0
Loans Originating In 2017 [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3],[4]	568.2
Loans Originating In 2017 [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	226.2
Loans Originating In 2017 [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	334.6
Loans Originating In 2017 [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[5]	2.0
Loans Originating In 2017 [Member] | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1]	630.3
Loans Originating In 2017 [Member] | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3],[4]	326.0
Loans Originating In 2017 [Member] | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	123.5
Loans Originating In 2017 [Member] | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	179.4
Loans Originating In 2017 [Member] | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[5]	1.4
Loans Originating In 2017 [Member] | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2]	500.7
Loans Originating In 2017 [Member] | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3],[4]	242.2
Loans Originating In 2017 [Member] | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	102.7
Loans Originating In 2017 [Member] | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	155.2
Loans Originating In 2017 [Member] | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[5]	0.6
Loans Originating In 2018 [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2]	2,571.0
Loans Originating In 2018 [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3],[4]	1,458.4
Loans Originating In 2018 [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	583.6
Loans Originating In 2018 [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	528.9
Loans Originating In 2018 [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[5]	0.1
Loans Originating In 2018 [Member] | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1]	1,459.4
Loans Originating In 2018 [Member] | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3],[4]	844.7
Loans Originating In 2018 [Member] | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	328.5
Loans Originating In 2018 [Member] | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	286.1
Loans Originating In 2018 [Member] | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[5]	0.1
Loans Originating In 2018 [Member] | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2]	1,111.6
Loans Originating In 2018 [Member] | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3],[4]	613.7
Loans Originating In 2018 [Member] | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	255.1
Loans Originating In 2018 [Member] | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	242.8
Loans Originating In 2018 [Member] | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[5]	0.0
Loans Originating In 2019 [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2]	4,235.7
Loans Originating In 2019 [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3],[4]	2,944.8
Loans Originating In 2019 [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	962.7
Loans Originating In 2019 [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	328.2
Loans Originating In 2019 [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[5]	0.0
Loans Originating In 2019 [Member] | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1]	2,366.0
Loans Originating In 2019 [Member] | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3],[4]	1,661.2
Loans Originating In 2019 [Member] | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	529.3
Loans Originating In 2019 [Member] | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	175.5
Loans Originating In 2019 [Member] | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[5]	0.0
Loans Originating In 2019 [Member] | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2]	1,869.7
Loans Originating In 2019 [Member] | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3],[4]	1,283.6
Loans Originating In 2019 [Member] | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	433.4
Loans Originating In 2019 [Member] | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	152.7
Loans Originating In 2019 [Member] | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[5]	0.0
Loans Originating In 2020 [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2]	1,229.6
Loans Originating In 2020 [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3],[4]	1,154.2
Loans Originating In 2020 [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	75.4
Loans Originating In 2020 [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[3]	0.0
Loans Originating In 2020 [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[2],[5]	0.0
Loans Originating In 2020 [Member] | Dealer Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1]	814.6
Loans Originating In 2020 [Member] | Dealer Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3],[4]	765.9
Loans Originating In 2020 [Member] | Dealer Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	48.7
Loans Originating In 2020 [Member] | Dealer Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[3]	0.0
Loans Originating In 2020 [Member] | Dealer Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[1],[5]	0.0
Loans Originating In 2020 [Member] | Purchased Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2]	415.0
Loans Originating In 2020 [Member] | Purchased Loans [Member] | Current, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3],[4]	388.3
Loans Originating In 2020 [Member] | Purchased Loans [Member] | Past Due 11-90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	26.7
Loans Originating In 2020 [Member] | Purchased Loans [Member] | Past Due Over 90 Days, Pre-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[3]	0.0
Loans Originating In 2020 [Member] | Purchased Loans [Member] | Post-term [Member]
Financing Receivable, Past Due [Line Items]
Loans receivable	[2],[5]	$ 0.0

[1] As Consumer Loans are aggregated by Dealer for purposes of recognizing revenue and evaluating impairment, 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 evaluating impairment, 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.