Common Stock and Stock Plans - Summary of Employee Stock Option Activity and TSR Performance Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Employee Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning Balance | shares	2,004,262
Number of Shares, Options granted | shares	53,000
Number of Shares, Options canceled | shares	(3,750)
Number of Shares, Options exercised | shares	(287,012)
Number of Shares, Outstanding, Ending Balance | shares	1,766,500
Number of Shares, Vested and exercisable, Ending Balance | shares	1,111,625
Weighted Average Exercise Price per Share, Outstanding, Beginning Balance | $ / shares	$ 58.99
Weighted Average Exercise Price per Share, Options granted | $ / shares	63.59
Weighted Average Exercise Price per Share, Options canceled | $ / shares	65.86
Weighted Average Exercise Price per Share, Options exercised | $ / shares	46.59
Weighted Average Exercise Price per Share, Outstanding, Ending Balance | $ / shares	61.13
Weighted Average Exercise Price per Share, Vested and exercisable, Ending Balance | $ / shares	$ 58.14
Weighted Average Remaining Contractual Term in Years, Outstanding	3 years 18 days
Weighted Average Remaining Contractual Term in Years, Vested and exercisable	2 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding | $	$ 10,279
Aggregate Intrinsic Value, Vested and exercisable | $	$ 9,185
TSR Performance Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Options granted | shares	497,500
Number of Shares, Outstanding, Ending Balance | shares	497,500
Weighted Average Exercise Price per Share, Options granted | $ / shares	$ 73.77
Weighted Average Exercise Price per Share, Outstanding, Ending Balance | $ / shares	$ 73.77
Weighted Average Remaining Contractual Term in Years, Outstanding	5 years 7 months 17 days