CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Increase (Decrease) in Shareholders' Equity [Roll Forward]
Proceeds from exercise of stock options (in shares)	332,665	324,140	447,250
Proceeds from exercise of stock options, tax benefits	$ 3,049,108	$ 2,072,030	$ 1,923,628
Common stock repurchases (in shares)	2,569,597	2,181,045	1,298,057
Issuance of restricted common stock under stock option plan (in shares)	524,500	60,416	54,951