Loans Receivable (Summary of Information Related to New Consumer Loan Assignments) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractual net cash flows at the time of assignment	[1]	$ 1,553.8		$ 1,599.5		$ 5,353.6		$ 5,290.2
Expected net cash flows at the time of assignment		1,208.9	[2]	1,253.0	[2]	4,105.2	[3]	4,153.6	[2]
Fair value at the time of assignment	[4]	852.1		894.4		2,912.5		2,955.0
Provision for Loan and Lease Losses		29.8		(19.3)		(464.3)		(49.2)
Expected future finance charges at the time of assignment	[5]	470.9		358.6		1,618.9		1,198.6
New Consumer Loan assignments				358.6	[6]			1,198.6
Realized Net Cash Flows		(1,173.1)	[2]	(1,047.5)	[2]	(3,419.4)	[7]	(3,125.3)	[7]
Expected net Loan income at the time of assignment	[8]	356.8		358.6		1,192.7		1,198.6
Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractual net cash flows at the time of assignment	[1]	823.0		895.1		2,787.2		2,982.2
Expected net cash flows at the time of assignment		733.6	[3]	797.3	[2]	2,471.7	[3]	2,661.0	[2]
Fair value at the time of assignment	[4]	519.0		573.3		1,751.1		1,901.1
Provision for Loan and Lease Losses		26.4		(17.9)		(202.8)		(44.0)
Expected future finance charges at the time of assignment	[5]	260.2		224.0		891.9		759.9
New Consumer Loan assignments				224.0	[6]			759.9
Realized Net Cash Flows		(733.0)	[2]	(687.4)	[2]	(2,168.6)	[7]	(2,080.7)	[7]
Expected net Loan income at the time of assignment	[8]	214.6		224.0		720.6		759.9
Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractual net cash flows at the time of assignment		730.8	[1]	704.4	[9]	2,566.4	[1]	2,308.0	[1]
Expected net cash flows at the time of assignment	[2]	475.3		455.7		1,633.5		1,492.6
Fair value at the time of assignment	[4]	333.1		321.1		1,161.4		1,053.9
Provision for Loan and Lease Losses		3.4		(1.4)		(261.5)		(5.2)
Expected future finance charges at the time of assignment	[5]	210.7		134.6		727.0		438.7
New Consumer Loan assignments				134.6	[6]			438.7
Realized Net Cash Flows		(440.1)	[2]	(360.1)	[2]	(1,250.8)	[7]	(1,044.6)	[7]
Expected net Loan income at the time of assignment	[8]	142.2		134.6		472.1		438.7
New Consumer Loan Assignments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Loan and Lease Losses		(114.1)		0.0		(426.2)		0.0
New Consumer Loan Assignments [Member] | Dealer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Loan and Lease Losses		(45.6)		0.0		(171.3)		0.0
New Consumer Loan Assignments [Member] | Purchased Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Loan and Lease Losses		$ (68.5)		$ 0.0		$ (254.9)		$ 0.0

[1] The Dealer Loans amount represents repayments that we were contractually owed at the time of assignment on Consumer Loans assigned under our Portfolio Program, less the related Dealer Holdback payments that we would be required to make if we collected all of the contractual repayments. The Purchased Loans amount represents repayments that we were contractually owed at the time of assignment on Consumer Loans assigned under our Purchase Program.

[2] The Dealer Loans amount represents repayments that we expected to collect at the time of assignment on Consumer Loans assigned under our Portfolio Program, less the related Dealer Holdback payments that we expected to make. The Purchased Loans amount represents repayments that we expected to collect at the time of assignment on Consumer Loans assigned under our Purchase Program.

[3] The Dealer Loans amount represents repayments that we expected to collect at the time of assignment on Consumer Loans assigned under our Portfolio Program, less the related Dealer Holdback payments that we expected to make. The Purchased Loans amount represents repayments that we expected to collect at the time of assignment on Consumer Loans assigned under our Purchase Program.

[4] The Dealer Loans amount represents advances paid to Dealers on Consumer Loans assigned under our Portfolio Program. The Purchased Loans amount represents one-time payments made to Dealers to purchase Consumer Loans assigned under our Purchase Program. The Loan amounts also represent the fair value at the time of assignment.

[5] Represents revenue that is expected to be recognized on a level-yield basis over the lives of the Loans.

[6] The Dealer Loans amount represents the net cash flows expected at the time of assignment on Consumer Loans assigned under our Portfolio Program, less the related advances paid to Dealers. The Purchased Loans amount represents the net cash flows expected at the time of assignment on Consumer Loans assigned under our Purchase Program, less the related one-time payments made to Dealers.

[7] The Dealer Loans amount represents repayments that we collected on Consumer Loans assigned under our Portfolio Program, less the Dealer Holdback and Accelerated Dealer Holdback payments that we made. Purchased Loans amount represents repayments that we collected on Consumer Loans assigned under our Purchase Program.

[8] Represents the amount that expected net cash flows at the time of assignment (2) exceed Loans receivable at the time of assignment (3).

[9] The Dealer Loans amount represents advances paid to Dealers on Consumer Loans assigned under our Portfolio Program. The Purchased Loans amount represents one-time payments made to Dealers to purchase Consumer Loans assigned under our Purchase Program.