Stock Based Compensation and Stock Options - Outstanding Options (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options outstanding, beginning balance	1,163,179	1,115,984	1,100,952
Granted, Number of Options	276,275	241,625	441,550
Exercised, Number of Options	(200,753)	(111,758)	(310,729)
Cancelled - forfeited, Number of Options	(115,300)
Cancelled - expired, Number of Options	(7,936)
Options outstanding, ending balance	1,115,465	1,163,179	1,115,984
Options vested and expected to vest, Number of Options	984,006
Ending exercisable, Number of Options	529,691
Options outstanding, Weighted Average Exercise per Share, beginning balance	$ 27.65	$ 24.80
Granted, Weighted Average Exercise Price per Share	35.51	37.64	$ 33.06
Exercised, Weighted Average Exercise Price per Share	19.75	17.27	15.31
Cancelled - forfeited, Weighted Average Exercise Price per Share	33.79
Cancelled - expired, Weighted Average Exercise Price per Share	30.10
Option outstanding, Weighted Average Exercise per Share, ending balance	30.36	$ 27.65	$ 24.80
Options vested and expected to vest, Weighted Average Exercise Price per Share	29.63
Ending exercisable, Weighted Average Exercise Price per Share	$ 24.93
Option outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 3 months 29 days
Options vested and expected to vest, Weighted Average Remaining Contractual Life (Years)	3 years 2 months 16 days
Ending exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 7 months 28 days
Option outstanding, Aggregate Intrinsic Value	$ 10,862,335
Options vested and expected to vest, Aggregate Intrinsic Value	10,337,930
Ending exercisable, Aggregate Intrinsic Value	$ 7,969,066