CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) (USD $)	Total	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), net [Member]
Balances at Mar. 31, 2012	$ 418,875,013	$ 65,630,753	$ 355,980,694	$ (2,736,434)
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Proceeds from exercise of stock options, including tax benefits	12,993,709	12,993,709
Common stock repurchases	(183,045,655)		(183,045,655)
Issuance of restricted common stock under stock option plan	3,842,674	3,842,674
Stock option expense	7,322,653	7,322,653
Other comprehensive income	2,318,117			2,318,117
Net income	104,089,748		104,089,748
Balances at Mar. 31, 2013	366,396,259	89,789,789	277,024,787	(418,317)
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Proceeds from exercise of stock options, including tax benefits	1,961,086	1,961,086
Common stock repurchases	(65,058,684)		(65,058,684)
Issuance of restricted common stock under stock option plan	3,635,047	3,635,047
Stock option expense	5,139,768	5,139,768
Other comprehensive income	(4,024,723)			(4,024,723)
Net income	44,676,970		44,676,970
Balances at Sep. 30, 2013	$ 352,725,723	$ 100,525,690	$ 256,643,073	$ (4,443,040)