Share-Based Compensation - Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Shares
Number of Shares, Outstanding Beginning Balance	5,164	5,537	5,720
Number of Shares, Granted	846	747	675
Number of Shares, Exercised	(827)	(1,118)	(855)
Number of Shares, Forfeited	(27)	(2)	(3)
Number of Shares, Outstanding Ending Balance	5,156	5,164	5,537
Number of Shares, Exercisable at December 31, 2015	2,311
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding (in dollar per share)	$ 64.43	$ 44.61	$ 34.66
Weighted Average Exercise Price, Granted (in dollars per share)	147.25	145.71	94.15
Weighted Average Exercise Price, Exercised (in dollars per share)	28.43	20.71	17.17
Weighted Average Exercise Price, Forfeited (in dollars per share)	95.33	19.61	37.44
Weighted Average Exercise Price, Outstanding (in dollars per share)	83.64	$ 64.43	$ 44.61
Weighted Average Exercise Price, Exercisable at December 31, 2015 (in dollars per share)	$ 58.07
Weighted Average Remaining Contractual Life (Years), Outstanding at December 31, 2015	7 years
Weighted Average Remaining Contractual Life (Years), Exercisable at December 31, 2015	6 years
Aggregate Intrinsic Value, Outstanding at December 31, 2015	$ 320,924
Aggregate Intrinsic Value, Exercisable at December 31, 2015	$ 198,460