Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Shares, Beginning balance (shares)	1,332,000	1,142,000	1,616,000
Number of Shares, Options granted (shares)	70,000	0	84,000
Number of Shares, Options assumed (shares)		586,000
Number of Shares, Options exercised (shares)	(180,000)	(350,000)	(465,000)
Number of Shares, Options cancelled / forfeited / expired (shares)	(50,000)	(46,000)	(93,000)
Number of Shares, Ending balance (shares)	1,172,000	1,332,000	1,142,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price Per Share, Beginning balance (usd per share)	$ 24.41	$ 20.63	$ 19.34
Weighted Average Exercise Price Per Share, Options granted (usd per share)	22.45		36.60
Weighted Average Exercise Price Per Share, Options assumed (usd per share)		29.05
Weighted Average Exercise Price Per Share, Options exercised (usd per share)	23.04	20.01	19.35
Weighted Average Exercise Price Per Share, Options cancelled / forfeited / expired (usd per share)	34.73	23.25	19.04
Weighted Average Exercise Price Per Share, Ending balance (usd per share)	$ 24.06	$ 24.41	$ 20.63
Weighted Average Remaining Contractual Life (in years)	3 years 6 months 7 days
Aggregate Intrinsic Value	$ 4,538
Vested and expected to vest, number of shares subject to options	1,138,000
Vested and expected to vest, weighted average remaining contractual life (in years)	3 years 4 months 17 days
Vested and expected to vest, aggregate intrinsic value	$ 4,482
Exercisable, number of shares subject to options	950,000
Exercisable, weighted average remaining contractual life (in years)	2 years 8 months 1 day
Exercisable, aggregate intrinsic value	$ 4,025