Loans Receivable (Summary of Changes in Loans Receivable) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Loans and Leases Receivable, Net [Roll Forward]
Balance, beginning of period	$ 2,518.1		$ 2,210.3		$ 2,408.2		$ 2,109.9
New Consumer Loan assignments	382.3	[1]	362.5	[1]	854.7	[1]	769.0	[1]
Principal collected on Loans receivable	(381.7)		(332.4)		(790.4)		(677.9)
Accelerated Dealer Holdback payments	(10.7)		(10.9)		(21.9)		(20.4)
Dealer Holdback payments	33.3		28.5		67.8		58.5
Transfers
Write-offs	(0.4)		(2.0)		(0.9)		(3.1)
Recoveries	0.5	[2]	0.7	[2]	1.0	[2]	1.3	[2]
Net change in other loans					0.5		0.4
Balance, end of period	2,562.8		2,278.5		2,562.8		2,278.5
Dealer Loans [Member]
Loans and Leases Receivable, Net [Roll Forward]
Balance, beginning of period	2,247.0		1,973.1		2,155.5		1,869.4
New Consumer Loan assignments	339.4	[1]	334.1	[1]	760.7	[1]	712.7	[1]
Principal collected on Loans receivable	(345.4)		(300.0)		(716.1)		(609.3)
Accelerated Dealer Holdback payments	(10.7)		(10.9)		(21.9)		(20.4)
Dealer Holdback payments	33.3		28.5		67.8		58.5
Transfers	(6.1)	[3]	(3.9)	[3]	(11.4)	[3]	(8.9)	[3]
Write-offs	(0.4)		(1.9)		(0.9)		(3.0)
Recoveries	0.5	[2]	0.6	[2]	1.0	[2]	1.2	[2]
Net change in other loans					0.5		0.4
Balance, end of period	2,279.0		2,041.4		2,279.0		2,041.4
Purchased Loans [Member]
Loans and Leases Receivable, Net [Roll Forward]
Balance, beginning of period	271.1		237.2		252.7		240.5
New Consumer Loan assignments	42.9	[1]	28.4	[1]	94.0	[1]	56.3	[1]
Principal collected on Loans receivable	(36.3)		(32.4)		(74.3)		(68.6)
Accelerated Dealer Holdback payments
Dealer Holdback payments
Transfers	6.1	[3]	3.9	[3]	11.4	[3]	8.9	[3]
Write-offs	0		(0.1)		0		(0.1)
Recoveries	0	[2]	0.1	[2]	0	[2]	0.1	[2]
Net change in other loans
Balance, end of period	$ 283.8		$ 237.1		$ 283.8		$ 237.1

[1] 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.

[2] Represents collections received on previously written off Loans.

[3] Under our Portfolio Program, certain events may result in Dealers forfeiting their rights to Dealer Holdback. We transfer the Dealer’s outstanding Dealer Loan balance to Purchased Loans in the period this forfeiture occurs.