Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Related Party Transaction [Line Items]
Affiliated Dealer Loan balances	$ 7.5				$ 7.5				$ 5.9
Percentage of Affiliated Dealer Loan balances	0.40%				0.40%				0.30%
New Consumer Loan assignments					1,048.0		968.7
Accelerated Dealer Holdback payments	(10.4)		(9.9)		(30.8)		(34.1)
Dealer Holdback payments	27.8		27.1		86.3		89.7
Affiliated Dealer Activity [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue	0.4		0.3		1.1		0.9
Dealer Loan revenue, percentage	0.30%		0.20%		0.30%		0.20%
New Consumer Loan assignments	1.1	[1]	1.0	[1]	3.5	[1]	2.7	[1]
New Consumer Loan assignments, percentage	0.30%	[1]	0.30%	[1]	0.30%	[1]	0.30%	[1]
Accelerated Dealer Holdback payments					0.1		0.1
Accelerated Dealer Holdback payments, percentage			0.80%		0.30%		0.40%
Dealer Holdback payments	$ 0.4		$ 0.6		$ 1.8		$ 2.6
Dealer Holdback payments, percentage	1.40%		2.60%		2.10%		2.90%

[1] Represents advances paid to Dealers on Consumer Loans assigned under our Portfolio Program and one-time payments made to Dealers to purchase Consumer Loans assigned under our Purchase Program.