Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net loss		$ (140,895)	$ (76,393)	$ (109,267)	$ (35,363)	$ (23,998)	$ (47,734)	$ (63,046)	$ 84,090	$ (361,918)	$ (50,688)	$ (267,265)
Weighted-average number of shares of common stock and common stock equivalents outstanding:
Weighted-average number of shares of common stock outstanding for computing basic loss per share						64,277	61,528	54,976	54,850	66,250	58,818	48,697
Dilutive effect of outstanding stock awards and stock options after application of the treasury stock method	[1]									0	0	0
Weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for computing diluted loss per share		68,653	66,209	65,484	64,631					66,250	58,818	48,697
Net loss per share — basic and diluted		$ (2.05)	$ (1.15)	$ (1.67)	$ (0.55)					$ (5.46)	$ (0.86)	$ (5.49)

[1] For the years ended December 31, 2018 and 2017, stock options, RSAs, RSUs, SARs and ESPP to purchase approximately 9.1 million and 9.4 million shares of common stock, respectively, were excluded from the net loss per share calculation as their effect would have been anti-dilutive. For the year ended December 31, 2016, stock options, RSAs and SARs to purchase approximately 5.7 million shares of common stock, were excluded from the net loss per share calculation as their effect would have been anti-dilutive. The Company accounts for the effect of the 2024 Notes on diluted net earnings per share using the if-converted method as they may be settled in cash or shares at the Company’s option. While the closing price on December 31, 2018 exceeded the conversion price of $73.42, the potential shares issuable under the 2024 Notes were excluded from the calculation of diluted loss per share as they were anti-dilutive using the if-converted method. In the period of conversion, the 2024 Notes will have no impact on diluted net earnings (loss) if they are settled in cash and will have an impact on diluted earnings per share if the Notes are settled in shares upon conversion and when the Company in an income position.