Stock Based Compensation and Stock Options - Outstanding Options (Detail) - USD ($)	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning balance	1,143,928	1,115,465
Granted, Number of Options	77,400	44,900
Exercised, Number of Options	(65,921)	(76,623)
Cancelled - forfeited, Number of Options	(2,062)
Cancelled - expired, Number of Options	(1,623)
Options outstanding, ending balance	1,151,722	1,074,521
Options vested and expected to vest, Number of Options	1,151,722
Ending exercisable, Number of Options	558,719
Options outstanding, beginning balance, Weighted Average Exercise Price	$ 32.02	$ 30.36
Granted, Weighted Average Exercise Price per Share	45.93	45.74
Exercised, Weighted Average Exercise Price per Share	26.67	22.11
Cancelled - forfeited, Weighted Average Exercise Price per Share	38.25
Cancelled - expired, Weighted Average Exercise Price per Share	42.99
Options outstanding, ending balance, Weighted Average Exercise Price	33.24	$ 31.56
Options vested and expected to vest, Weighted Average Exercise Price per Share	33.24
Ending exercisable, Weighted Average Exercise Price per Share	$ 28.46
Option outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 1 month 9 days
Options vested and expected to vest, Weighted Average Remaining Contractual Life (Years)	3 years 1 month 9 days
Ending exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 1 month 16 days
Option outstanding, Aggregate Intrinsic Value	$ 16,370,972
Options vested and expected to vest, Aggregate Intrinsic Value	16,370,972
Ending exercisable, Aggregate Intrinsic Value	$ 10,608,043