Summary of Significant Accounting Policies - Summary of change to consolidated statements of cash flows (operating activities) (Details 3) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Consolidated Statements of Cash Flows (Operating Activities)
Net income	$ 19,940,946	$ 22,221,759	$ 16,768,294
Provision for credit losses	13,391,875	12,367,593	15,611,544
Deferred income taxes	696,339	245,273	(1,440,668)
Amortization of dealer discounts	(11,482,251)	(12,348,448)	(10,941,553)
Net cash provided by operating activities	25,620,155	21,874,879	21,357,624
Reported
Consolidated Statements of Cash Flows (Operating Activities)
Net income		22,230,292	16,805,184
Provision for credit losses		5,319	4,610,221
Deferred income taxes		250,566	(1,417,788)
Amortization of dealer discounts
Net cash provided by operating activities		21,874,879	21,357,624
Correction
Consolidated Statements of Cash Flows (Operating Activities)
Net income		(8,533)	(36,890)
Provision for credit losses		12,362,274	11,001,323
Deferred income taxes		(5,293)	(22,880)
Amortization of dealer discounts		(12,348,448)	(10,941,553)
Net cash provided by operating activities