Stock-Based Compensation and Stock Options - Stock Options (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options outstanding, beginning balance	1,151,722	1,074,521	1,143,928	1,115,465
Options granted, Shares	73,650	45,600	151,050	90,500
Options exercised, Shares	(145,911)	(14,593)	(211,832)	(91,216)
Options cancelled/forfeited, Shares	(10,958)	(2,609)	(14,643)	(11,830)
Options outstanding, ending balance	1,068,503	1,102,919	1,068,503	1,102,919
Options outstanding, beginning balance, Weighted Average Exercise Price	$ 33.24	$ 31.56	$ 32.02	$ 28.81
Options granted, Weighted Average Exercise Price	48.35	43.32	47.11	44.52
Options exercised, Weighted Average Exercise Price	25.60	20.61	25.93	21.87
Options cancelled/forfeited, Weighted Average Exercise Price	38.39	39.33	39.28	36.36
Options outstanding, ending balance, Weighted Average Exercise Price	$ 35.28	$ 32.17	$ 35.28	$ 32.17