Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 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									0.30%
New Consumer Loan assignments					1,103.6		1,048.0
Accelerated Dealer Holdback payments	9.7		10.4		31.6		30.8
Dealer Holdback payments	33.7		27.8		101.5		86.3
Affiliated Dealer Activity [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue	0.4		0.4		1.2		1.1
Dealer Loan revenue, percentage	0.30%		0.30%		0.30%		0.30%
New Consumer Loan assignments	0.9	[1]	1.1	[1]	3.0	[1]	3.5	[1]
New Consumer Loan assignments, percentage	0.20%	[1]	0.30%	[1]	0.20%	[1]	0.30%	[1]
Accelerated Dealer Holdback payments	0				0.1		0.1
Accelerated Dealer Holdback payments, percentage	0.00%		0.00%		0.30%		0.30%
Dealer Holdback payments	$ 0.3		$ 0.4		$ 1.1		$ 1.8
Dealer Holdback payments, percentage	0.90%		1.40%		1.10%		2.10%

[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.