Stock Based Compensation and Stock Options - Outstanding Options (Detail) - USD ($)	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options outstanding, beginning balance	1,115,465	1,163,179
Granted, Number of Options	44,900	39,700
Exercised, Number of Options	(76,623)	(35,837)
Cancelled - forfeited, Number of Options	(9,139)
Cancelled - expired, Number of Options	(82)
Options outstanding, ending balance	1,074,521	1,167,042
Options vested and expected to vest, Number of Options	939,647
Ending exercisable, Number of Options	493,994
Options outstanding, beginning Average Price	$ 30.36	$ 27.65
Granted, Weighted Average Exercise Price per Share	45.74	34.67
Exercised, Weighted Average Exercise Price per Share	22.11	19.16
Cancelled - forfeited, Weighted Average Exercise Price per Share	35.34
Cancelled - expired, Weighted Average Exercise Price per Share	44.78
Option outstanding, Weighted Average Exercise Price per Share, ending balance	31.56	$ 28.15
Options vested and expected to vest, Weighted Average Exercise Price per Share	30.83
Ending exercisable, Weighted Average Exercise Price per Share	$ 25.98
Option outstanding, Weighted Average Remaining Contractual Life (Years)	3 years 3 months 11 days
Options vested and expected to vest, Weighted Average Remaining Contractual Life (Years)	3 years 2 months 1 day
Ending exercisable, Weighted Average Remaining Contractual Life (Years)	2 years 7 months 10 days
Option outstanding, Aggregate Intrinsic Value	$ 12,787,075
Options vested and expected to vest, Aggregate Intrinsic Value	11,874,296
Ending exercisable, Aggregate Intrinsic Value	$ 8,598,614