Stock Option Activity (Detail)	3 Months Ended
	Jun. 30, 2019 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding Options at Beginning of Year | shares	1,042,925
Number of Shares, Granted | shares	184,892
Number of Shares, Exercised | shares	(5,181)
Number of Shares, Cancelled | shares	(7,883)
Number of Shares, Outstanding Options at End of Year | shares	1,214,753
Number of Shares, Options Exercisable at End of Year | shares	808,899
Weighted-Average Exercise Price, Outstanding Options at Beginning of Year	$ 76.88
Weighted-Average Exercise Price, Granted	91.58
Weighted-Average Exercise Price, Exercised	76.53
Weighted-Average Exercise Price, Cancelled	106.24
Weighted-Average Exercise Price, Outstanding Options at End of Year	78.95
Weighted-Average Exercise Price, Options Exercisable at End of Period	72.08
Weighted Average Fair Value of Options Granted During the Year	$ 27.37