Finance Receivables - Reconciliation of changes in allowance for credit losses on direct loans (Details 3) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Provision for credit losses	$ 7,513	$ 7,599	$ 6,177	$ 4,989	$ 5,188	$ 5,797	$ 5,154	$ 4,232	$ 26,278	$ 20,371	$ 14,979
Finance receivables | Direct Loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of year			$ 748				$ 703		703	590	468
Provision for credit losses									352	362	285
Losses absorbed									(328)	(277)	(192)
Recoveries									21	28	29
Balance at end of year				$ 748				$ 703	$ 748	$ 703	$ 590