Related Party Transactions (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		Dec. 31, 2013
Related Party Transaction [Line Items]
Affiliated Dealer Loan balances	$ 8.0				$ 8.0				$ 7.5
Percentage of Affiliated Dealer Loan balances	0.40%				0.40%				0.30%
New Consumer Loan assignments					760.7		712.7
Accelerated Dealer Holdback payments	10.7		10.9		21.9		20.4
Dealer Holdback payments	33.3		28.5		67.8		58.5
Affiliated Dealer Activity [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue	0.4		0.4		0.8		0.7
Dealer Loan revenue, percentage	0.30%		0.30%		0.30%		0.30%
New Consumer Loan assignments	1.0	[1]	1.3	[1]	2.1	[1]	2.4	[1]
New Consumer Loan assignments, percentage	0.30%	[1]	0.40%	[1]	0.20%	[1]	0.30%	[1]
Accelerated Dealer Holdback payments	0.1		0.1		0.1		0.1
Accelerated Dealer Holdback payments, percentage	0.90%		0.90%		0.50%		0.50%
Dealer Holdback payments	$ 0.4		$ 0.8		$ 0.8		$ 1.4
Dealer Holdback payments, percentage	1.20%		2.80%		1.20%		2.40%

[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.