Summary of Stock Option Activity (Detail) - Stock Option Awards $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Options outstanding, shares
Beginning Balance | shares	1,480
Granted | shares	30
Exercised | shares	(13)
Forfeited/Expired | shares	(37)
Ending Balance | shares	1,460
Exercisable as of March 31, 2019 | shares	814
Expected to vest as of March 31, 2019 | shares	646
Total | shares	1,460
Weighted Average Exercise Price Per Share
Beginning Balance | $ / shares	$ 137.16
Granted | $ / shares	145.41
Exercised | $ / shares	120.59
Forfeited/Expired | $ / shares	140.98
Ending Balance | $ / shares	137.38
Exercisable as of March 31, 2019 | $ / shares	137.00
Expected to vest as of March 31, 2019 | $ / shares	137.85
Total | $ / shares	$ 137.38
Aggregate Intrinsic Value
Exercised | $	$ 245
Exercisable as of March 31, 2019 | $	12,929
Expected to vest as of March 31, 2019 | $	7,628
Total | $	$ 20,557
Weighted Average Remaining Contractual Term (Years)
Exercisable as of March 31, 2019	5 years 10 months 24 days
Expected to vest as of March 31, 2019	8 years 10 months 24 days
Total	7 years 2 months 12 days