Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended						9 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net loss		$ (126,326)	$ (276,403)	$ (76,643)	$ (76,393)	$ (109,267)	$ (35,363)	$ (479,372)	$ (221,023)
Weighted-average common shares outstanding - basic		74,177			66,209			73,298	65,454
Effect of dilutive securities*	[1]	0			0			0	0
Weighted-average common shares outstanding - diluted		74,177			66,209			73,298	65,454
Net loss per share - basic and diluted		$ (1.70)			$ (1.15)			$ (6.54)	$ (3.38)

[1] For the three and nine months ended September 30, 2019 and 2018, stock options, RSAs, RSUs, and ESPP to purchase 9.6 million and 9.2 million shares of the Company’s common stock, respectively, were excluded from the diluted 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 September 30, 2019 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.