Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Options Outstanding, Shares
Beginning Balance	886,000
Granted	90,000	0
Exercised	(7,000)
Forfeited/Expired	(30,000)
Ending Balance	939,000
Exercisable as of March 31, 2017	374,000
Expected to vest as of March 31, 2017	565,000
Total	939,000
Weighted Average Exercise Price Per Share
Beginning Balance	$ 143.89
Granted	189.16
Exercised	160.88
Forfeited/Expired	201.25
Ending Balance	146.27
Exercisable as of March 31, 2017	137.67
Expected to vest as of March 31, 2017	151.97
Total	$ 146.27
Aggregate Intrinsic Value
Exercised	$ 212
Exercisable as of March 31, 2017	19,119
Expected to vest as of March 31, 2017	21,073
Total	$ 40,192
Weighted Average Remaining Contractual Term (Years)
Exercisable as of March 31, 2017	7 years 4 months 24 days
Expected to vest as of March 31, 2017	7 years 10 months 24 days
Total	7 years 8 months 12 days