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, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Earnings Per Share [Abstract]
Net loss	$ (41,851)		$ (33,874)		$ (103,410)		$ (62,147)
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	41,357		39,862		41,341		38,847
Dilutive effect of outstanding warrants, stock awards and stock options after application of the treasury stock method	0	[1]	0	[2]	0	[1]	0	[2]
Weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for computing diluted loss per share	41,357		39,862		41,341		38,847
Net loss per share - basic and diluted	$ (1.01)		$ (0.85)		$ (2.50)		$ (1.60)

[1] For the three and six months ended June 30, 2015, stock options, restricted stock awards and stock appreciation rights to purchase approximately 7.0 million shares of common stock were excluded from the net loss per share calculation as their effect would have been anti-dilutive.

[2] For the three and six months ended June 30, 2014, warrants, stock options, restricted stock awards, restricted stock units and stock appreciation rights to purchase approximately 5.9 million shares of common stock were excluded from the net loss per share calculation as their effect would have been anti-dilutive.