Net Loss Per Common Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted Average Shares (Detail) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	21,245	20,447
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	2,407	2,777
4.50% Convertible Senior Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	25,000