Stock Based Compensation and Stock Options - Outstanding Options (Detail) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning, Shares	1,191,251	1,264,530	1,100,930	1,502,046
Granted, Number of Options	142,650	33,300	382,650	96,700
Exercised, Number of Options	(69,276)	(57,876)	(188,327)	(261,234)
Cancelled - forfeited, Number of Options	(2,703)
Cancelled - expired, Number of Options	(1,354)
Options outstanding, ending, Shares	1,260,568	1,191,588	1,260,568	1,191,588
Ending vested and expected to vest, Number of Options	1,075,586		1,075,586
Ending exercisable, Number of Options	467,790		467,790
Options outstanding, beginning, Average Price	$ 20.39	$ 17.71	$ 18.65	$ 17.10
Granted, Weighted Average Exercise Per Share	$ 40.24	$ 21.61	$ 31.14	$ 21.56
Exercised, Weighted Average Exercise Per Share	$ 16.33	$ 12.45	$ 15.14	$ 12.54
Cancelled - forfeited, Weighted Average Exercise Per Share	$ 26.40
Cancelled - expired, Weighted Average Exercise Per Share	$ 12.91
Options outstanding, ending, Average Price	$ 22.85	$ 17.88	$ 22.85	$ 17.88
Ending vested and expected to vest, Weighted Average Exercise Per Share	$ 21.66		$ 21.66
Ending exercisable, Weighted Average Exercise Per Share	$ 15.71		$ 15.71
Ending outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 7 months 2 days
Ending vested and expected to vest, Weighted Average Remaining Contractual Life (Years)	3 years 5 months 16 days
Ending exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 8 months 23 days
Ending outstanding, Aggregate Intrinsic Value	$ 30,062,229		$ 30,062,229
Ending vested and expected to vest, Aggregate Intrinsic Value	26,935,727		26,935,727
Ending exercisable, Aggregate Intrinsic Value	$ 14,497,528		$ 14,497,528