CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) (USD $)	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), net [Member]	Total
Balances at Mar. 31, 2011	$ 47,352,738	$ 395,086,232	$ 136,199	$ 442,575,169
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Proceeds from exercise of stock options, including tax benefits	11,660,188	0	0	11,660,188
Common stock repurchases	0	(139,799,981)	0	(139,799,981)
Issuance of restricted common stock under stock option plan	1,750,596	0	0	1,750,596
Stock option expense	4,867,231	0	0	4,867,231
Other comprehensive income	0	0	(2,872,633)	(2,872,633)
Net income	0	100,694,443	0	100,694,443
Balances at Mar. 31, 2012	65,630,753	355,980,694	(2,736,434)	418,875,013
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Proceeds from exercise of stock options, including tax benefits	2,499,335	0	0	2,499,335
Common stock repurchases	0	(61,731,794)	0	(61,731,794)
Issuance of restricted common stock under stock option plan	677,818	0	0	677,818
Stock option expense	1,172,910	0	0	1,172,910
Other comprehensive income	0	0	(2,248,231)	(2,248,231)
Net income	0	22,614,998	0	22,614,998
Balances at Jun. 30, 2012	$ 69,980,816	$ 316,863,898	$ (4,984,665)	$ 381,860,049