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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss		$ (64,681)	$ (51,939)	$ (41,851)	$ (61,559)	$ (44,416)	$ (29,226)	$ (33,874)	$ (28,273)	$ (220,030)	$ (135,789)	$ (111,985)
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										42,290	40,026	33,850
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		44,882	41,565	41,357	41,324	41,304	41,066	39,862	37,821	42,290	40,026	33,850
Net loss per share — basic and diluted		$ (1.44)	$ (1.25)	$ (1.01)	$ (1.49)	$ (1.08)	$ (0.71)	$ (0.85)	$ (0.75)	$ (5.20)	$ (3.39)	$ (3.31)

[1] For the year ended December 31, 2015 and 2014, stock options, RSAs and SARs to purchase approximately 6.8 million and 5.4 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 2013, stock options, RSAs, RSUs, SARs and warrants to purchase approximately 5.2 million shares of common stock were excluded from the net loss per share calculation as their effect would have been anti-dilutive.