The Company and Significant Accounting Policies - Reconciliation of Basic and Diluted Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share Basic And Diluted [Abstract]
Net income (loss)	$ 2,215	$ 157,208	$ 5,248	$ 163,321
Denominator:
Weighted average common shares outstanding, basic	88,852,342	90,517,492	89,371,750	90,370,679
Basic earnings per share:
Net income (loss) per share	$ 0.02	$ 1.74	$ 0.06	$ 1.81
Denominator:
Weighted average common shares outstanding, basic	88,852,342	90,517,492	89,371,750	90,370,679
Dilutive securities:
Stock options and restricted stock units	1,270,083	1,643,616	1,202,913	1,615,267
Weighted average common shares outstanding, diluted	90,122,425	92,161,108	90,574,663	91,985,946
Diluted earnings per share:
Net income (loss) per share	$ 0.02	$ 1.71	$ 0.06	$ 1.78