Summary of Significant Accounting Policies (Detail Textuals 1) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Unearned interest, dealer discounts and allowance for credit losses	$ 195,500	$ 186,300	$ 195,500	$ 186,300
Period for maintaining historical write off information with respect to static pool			10 years
Percentage of liquidation level assist in determining allowance for credit losses			20.00%
Percentage of liquidation level assist in determining allowance for credit losses			40.00%
Percentage of liquidation level assist in determining allowance for credit losses			60.00%
Percentage of liquidation level assist in determining allowance for credit losses			80.00%
Percentage of liquidation level assist in determining allowance for credit losses			100.00%
Percentage of allowances increased of principal amount			50.00%
Average dealer discount associated with new volume			7.08%	7.51%	8.08%
Cash paid for income taxes			$ 5,400	$ 8,500	$ 7,300
Cash paid for interest, including debt origination costs			9,100	8,800	6,100
Amortization of commission for products	$ (1,754)	$ (1,662)	$ (1,754)	$ (1,662)	$ (1,266)