Share-Based Compensation - Summary of Stock Option Activity Plans (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Number of Options Outstanding
Number of Options Outstanding, Beginning Balance	7,384	8,048	9,158
Number of Options Outstanding, Granted	25	547	1,881
Number of Options Outstanding, Exercised	(1,722)	(962)	(2,323)
Number of Options Outstanding, Canceled/Forfeited	(401)	(249)	(668)
Number of Options Outstanding, Ending Balance	5,286	7,384	8,048	9,158
Number of Options Outstanding, Vested and expected to vest	5,210
Number of Options Outstanding, Exercisable	4,609
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning Balance	$ 10.59	$ 10.27	$ 8.23
Weighted-Average Exercise Price Per Share, Granted	23.99	16.53	16.35
Weighted-Average Exercise Price Per Share, Exercised	10.39	10.01	6.82
Weighted-Average Exercise Price Per Share, Canceled/Forfeited	16.04	15.50	11.42
Weighted-Average Exercise Price Per Share, Ending Balance	10.30	$ 10.59	$ 10.27	$ 8.23
Weighted-Average Exercise Price Per Share, Vested and expected to vest	10.21
Weighted-Average Exercise Price Per Share, Exercisable	$ 9.41
Weighted-Average Contractual Term
Weighted-Average Contractual Term	4 years 2 months 12 days	5 years 3 months 18 days	6 years 2 months 12 days	7 years 2 months 12 days
Weighted-Average Contractual Term, Vested and expected to vest	4 years 2 months 12 days
Weighted-Average Contractual Term, Exercisable	4 years 1 month 6 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding	$ 201,480	$ 74,065	$ 107,091	$ 61,367
Aggregate Intrinsic Value, Vested and expected to vest	199,000
Aggregate Intrinsic Value, Exercisable	$ 179,743