Basic and Diluted Net Loss Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Earnings Per Share [Abstract]
Net loss	$ (44,416)	$ (29,226)	$ (33,874)	$ (28,273)	$ (8,820)	$ (42,030)	$ (19,051)	$ (42,084)	$ (135,789)		$ (111,985)		$ (121,287)
Weighted-average number of shares of common stock and common stock equivalents outstanding:
Weighted-average number of common stock outstanding for computing basic net loss per share									40,026		33,850		23,602
Dilutive effect of outstanding warrants and stock awards after application of the treasury stock method									0	[1]	0	[1]	0	[1]
Weighted-average number of common stock outstanding for computing diluted net loss per share	41,304	41,066	39,862	37,821	37,596	33,943	31,984	31,813	40,026		33,850		23,602
Net loss per share-basic and diluted	$ (1.08)	$ (0.71)	$ (0.85)	$ (0.75)	$ (0.23)	$ (1.24)	$ (0.60)	$ (1.32)	$ (3.39)		$ (3.31)		$ (5.14)

[1] Warrants, stock options, restricted stock units and stock appreciation rights to purchase approximately 5,386,203, 5,158,382 and 5,858,000 shares of common stock as of December 31, 2014, 2013 and 2012, respectively, were excluded from the net loss per share calculation as their effect would have been anti-dilutive.