Net Income (Loss) Per Share - Schedule of Basic and Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Weighted average common shares outstanding	49,253	49,203	51,841
Unvested common shares subject to repurchase	(2)	(16)	(39)
Total common shares-basic	49,251	49,187	51,802
Options	0	357	343
Restricted stock awards and units	0	646	441
Total common shares-diluted	49,251	50,190	52,586