Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Related Party Transaction [Line Items]
Affiliated Dealer Loan balances	$ 7.3				$ 7.3				$ 5.9
Percentage of Affiliated Dealer Loan balances	0.40%				0.40%				0.30%
New Consumer Loan assignments					712.7		675.4
Accelerated Dealer Holdback payments	(10.9)		(11.3)		(20.4)		(24.2)
Dealer Holdback payments	28.5		29.4		58.5		62.6
Affiliated Dealer Activity [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue	0.4		0.3		0.7		0.6
Dealer Loan revenue, percentage	0.30%		0.20%		0.30%		0.30%
New Consumer Loan assignments	1.3	[1]	0.5	[1]	2.4	[1]	1.7	[1]
New Consumer Loan assignments, percentage	0.40%	[1]	0.20%	[1]	0.30%	[1]	0.20%	[1]
Accelerated Dealer Holdback payments	0.1				0.1		0.1
Accelerated Dealer Holdback payments, percentage	0.90%		0.00%		0.50%		0.30%
Dealer Holdback payments	$ 0.8		$ 1.0		$ 1.4		$ 2.0
Dealer Holdback payments, percentage	2.80%		3.30%		2.40%		3.10%

[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.