Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Related Party Transaction [Line Items]
Affiliated Dealer Loan balances	$ 6.5				$ 5.9
Percentage of Affiliated Dealer Loan balances	0.30%				0.30%
New Consumer Loan assignments	378.6		374.4
Accelerated Dealer Holdback payments	(9.5)		(12.9)
Dealer Holdback payments	30.0		33.2
Affiliated Dealer Activity [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue	0.3		0.3
Dealer Loan revenue, percentage	0.20%		0.30%
New Consumer Loan assignments	1.1	[1]	1.2	[1]
New Consumer Loan assignments, percentage	0.30%	[1]	0.30%	[1]
Accelerated Dealer Holdback payments			0.1
Accelerated Dealer Holdback payments, percentage	0.30%		0.50%
Dealer Holdback payments	$ 0.6		$ 1.0
Dealer Holdback payments, percentage	2.00%		3.00%

[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.