Stock Based Compensation and Stock Options - Outstanding Options (Detail) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options outstanding, beginning balance	1,136,073	1,191,251	1,115,984	1,100,930
Granted, Number of Options	122,825	142,650	208,875	382,650
Exercised, Number of Options	(21,734)	(69,276)	(78,684)	(188,327)
Cancelled - forfeited, Number of Options	0
Cancelled - expired, Number of Options	0
Options outstanding, ending balance	1,237,164	1,260,568	1,237,164	1,260,568
Ending vested and expected to vest, Number of Options	1,078,621		1,078,621
Ending exercisable, Number of Options	514,993		514,993
Options outstanding, beginning Average Price	$ 26.42	$ 20.39	$ 24.80	$ 18.65
Granted, Weighted Average Exercise Per Share	$ 34.78	$ 40.24	$ 37.93	$ 31.14
Exercised, Weighted Average Exercise Per Share	$ 15.27	$ 16.33	$ 17.54	$ 15.14
Cancelled - forfeited, Weighted Average Exercise Per Share	$ 0
Cancelled - expired, Weighted Average Exercise Per Share	$ 0
Options outstanding, ending Average Price	$ 27.45	$ 22.85	$ 27.45	$ 22.85
Ending vested and expected to vest, Weighted Average Exercise Per Share	$ 26.28		$ 26.28
Ending exercisable, Weighted Average Exercise Per Share	$ 19.72		$ 19.72
Options outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 6 months
Ending vested and expected to vest, Weighted Average Remaining Contractual Life (Years)	3 years 4 months 21 days
Ending exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 10 months 6 days
Ending outstanding, Aggregate Intrinsic Value	$ 13,429,112		$ 13,429,112
Ending vested and expected to vest, Aggregate Intrinsic Value	12,851,985		12,851,985
Ending exercisable, Aggregate Intrinsic Value	$ 9,041,701		$ 9,041,701