Description of Business (Percentage of Consumer Loans Assigned Based on Volumes) (Details)		3 Months Ended
		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Portfolio Program [Member]
Description Of Business [Line Items]
Percentage of new consumer loans unit volume		71.90%	72.30%	73.30%	76.90%	76.20%	77.80%	82.40%
Percentage of new consumer loans dollar volume	[1]	68.60%	67.90%	67.80%	71.10%	68.50%	69.80%	75.60%
Purchase Program [Member]
Description Of Business [Line Items]
Percentage of new consumer loans unit volume		28.10%	27.70%	26.70%	23.10%	23.80%	22.20%	17.60%
Percentage of new consumer loans dollar volume	[1]	31.40%	32.10%	32.20%	28.90%	31.50%	30.20%	24.40%

[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. Payments of Dealer Holdback and accelerated Dealer Holdback are not included.