Net Loss Per Common Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted Average Shares (Detail) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	20,547	20,355
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	2,402	2,777
Conversion premium on the Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	25,000	25,000