Related Party Transactions (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Affiliated Dealer Loan balances		$ 15.0		$ 12.6
Percentage of Affiliated Dealer Loan balances		0.50%		0.40%
New Consumer Loan assignments		$ 562.7	$ 533.5
Accelerated Dealer Holdback payments		14.8	13.8
Dealer Holdback payments		39.9	41.1
Affiliated Dealer Activity [Member]
Related Party Transaction [Line Items]
Dealer Loan revenue		$ 0.7	$ 0.4
Dealer Loan revenue, percentage		0.40%	0.30%
New Consumer Loan assignments	[1]	$ 4.6	$ 1.5
New Consumer Loan assignments, percentage	[1]	0.60%	0.20%
Accelerated Dealer Holdback payments		$ 0.1	$ 0.1
Accelerated Dealer Holdback payments, percentage		0.90%	0.70%
Dealer Holdback payments		$ 0.3	$ 0.3
Dealer Holdback payments, percentage		0.80%	0.70%

[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.