Description of Business (Percentage of Consumer Loans Assigned Based on Volumes) (Details)		3 Months Ended
		Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Portfolio Program [Member]
Description Of Business [Line Items]
Percentage of new consumer loans unit volume		66.70%	67.40%	69.40%	69.50%	69.70%	70.10%
Percentage of new consumer loans dollar volume	[1]	63.70%	65.00%	67.40%	67.00%	66.80%	67.40%
Purchase Program [Member]
Description Of Business [Line Items]
Percentage of new consumer loans unit volume		33.30%	32.60%	30.60%	30.50%	30.30%	29.90%
Percentage of new consumer loans dollar volume	[1]	36.30%	35.00%	32.60%	33.00%	33.20%	32.60%

[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 (as defined below) and accelerated Dealer Holdback are not included.