CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY AND COMPREHENSIVE INCOME (LOSS) (Unaudited) (USD $)	Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total	Total Comprehensive Income [Member]
Balances at Mar. 31, 2010	$ 27,112,822	$ 357,179,568	$ (1,344,436)	$ 382,947,954
Proceeds from exercise of stock options , including tax benefits	13,806,260	0	0	13,806,260
Common stock repurchases	0	(53,342,516)	0	(53,342,516)
Issuance of restricted common stock under stock option plan	1,485,359	0	0	1,485,359
Stock option expense	3,855,348	0	0	3,855,348
Proceeds from the sale of the call option and warrants associated with the convertible notes	1,092,949	0	0	1,092,949
Other comprehensive income (Loss)	0	0	1,480,635	1,480,635	1,480,635
Net income	0	91,249,180	0	91,249,180	91,249,180
Total comprehensive income	0	0	0	0	92,729,815
Balances at Mar. 31, 2011	47,352,738	395,086,232	136,199	442,575,169
Proceeds from exercise of stock options , including tax benefits	9,375,695	0	0	9,375,695
Common stock repurchases	0	(73,983,889)	0	(73,983,889)
Issuance of restricted common stock under stock option plan	1,180,922	0	0	1,180,922
Stock option expense	3,716,308	0	0	3,716,308
Other comprehensive income (Loss)	0	0	(6,421,480)	(6,421,480)	(6,421,480)
Net income	0	63,067,857	0	63,067,857	63,067,857
Total comprehensive income	0	0	0	0	56,646,377
Balances at Dec. 31, 2011	$ 61,625,663	$ 384,170,200	$ (6,285,281)	$ 439,510,582