Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net loss		$ (276,403)	$ (76,643)	$ (109,267)	$ (35,363)	$ (353,046)	$ (144,630)
Weighted-average common shares outstanding - basic		73,958		65,484		72,850	65,060
Effect of dilutive securities*	[1]	0		0		0	0
Weighted-average common shares outstanding - diluted		73,958		65,484		72,850	65,060
Net loss per share - basic and diluted		$ (3.74)		$ (1.67)		$ (4.85)	$ (2.22)

[1] For the three and six months ended June 30, 2019 and 2018, stock options, RSAs, RSUs, stock appreciation rights (“SAR”) to purchase 9.7 million and 9.4 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.