Stockholders' Equity - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Number of Units outstanding, beginning of year (in shares) | shares	2,348
Number of Units, Granted (in shares) | shares	341
Number of Units, Released (in shares) | shares	(556)
Number of Units, Forfeited (in shares) | shares	(248)
Number of Units outstanding, end of period (in shares) | shares	1,885
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value, Units outstanding, beginning of year (in dollars per share) | $ / shares	$ 23.47
Weighted Average Grant Date Fair Value, Granted (in dollars per share) | $ / shares	45.52
Weighted Average Grant Date Fair Value, Released (in dollars per share) | $ / shares	23.62
Weighted Average Grant Date Fair Value, Forfeited (in dollars per share) | $ / shares	23.79
Weighted Average Grant Date Fair Value, Units outstanding, end of period (in dollars per share) | $ / shares	$ 27.45
Aggregate intrinsic value at end of period | $	$ 128,991