Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended						9 Months Ended
		Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net loss		$ (48,144)	$ (81,405)	$ (167,250)	$ (196,499)	$ (150,820)	$ (17,492)	$ (296,799)	$ (364,811)
Weighted-average common shares outstanding - basic		79,880			78,501			79,695	77,637
Effect of dilutive securities*	[1]	0			0			0	0
Weighted-average common shares outstanding - diluted		79,880			78,501			79,695	77,637
Net loss per share - basic and diluted		$ (0.60)			$ (2.50)			$ (3.72)	$ (4.70)

[1] For both the three and nine months ended September 30, 2021 and 2020, stock options, restricted stock awards, restricted stock units, and employee stock purchase plan to purchase 9.6 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 this obligation may be settled in cash or shares at the Company’s option. The effect of potential share settlement is included in the diluted EPS calculation if the effect is more dilutive. During the three and nine months ended September 30, 2021, the inclusion of the potential share settlement of the 2024 Notes was anti-dilutive.