Employee Stock-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Summarizes stock option activity
Options, Outstanding Number, Beginning Balance | shares	4,998
Options, Granted | shares	63
Options, Exercised | shares	(1,496)
Options, Forfeited | shares	(50)
Options, Outstanding Number, Ending Balance | shares	3,515
Exercisable Options, Outstanding Number, Ending Balance | shares	2,489
Weighted Average Exercise Price, Beginning Balance | $ / shares	$ 5.19
Weighted Average Exercise Price, Granted | $ / shares	6.59
Weighted Average Exercise Price, Exercised | $ / shares	4.43
Weighted Average Exercise Price, Forfeited | $ / shares	7.49
Weighted Average Exercise Price, Ending Balance | $ / shares	5.51
Exercisable, Weighted Average Exercise Price, Ending Balance | $ / shares	$ 4.71
Weighted Average Remaining Years, Outstanding	5 years 4 months 24 days
Weighted Average Remaining Years, Exercisable	4 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding | $	$ 19,184
Exercisable, Aggregate Intrinsic Value | $	$ 15,592