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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss		$ (88,452)	$ (56,742)	$ (62,301)	$ (59,770)	$ (64,681)	$ (51,939)	$ (41,851)	$ (61,559)	$ (267,265)	$ (220,030)	$ (135,789)
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										48,697	42,290	40,026
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		54,619	48,254	46,157	45,697	44,882	41,565	41,357	41,324	48,697	42,290	40,026
Net loss per share — basic and diluted		$ (1.62)	$ (1.18)	$ (1.35)	$ (1.31)	$ (1.44)	$ (1.25)	$ (1.01)	$ (1.49)	$ (5.49)	$ (5.20)	$ (3.39)

[1] For the year ended December 31, 2016 and 2015, stock options, RSAs and SARs to purchase approximately 5.7 million and 6.8 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 2014, stock options, RSAs, RSUs, SARs and warrants to purchase approximately 5.4 million shares of common stock were excluded from the net loss per share calculation as their effect would have been anti-dilutive.