Net Loss Per Common Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted Average Shares (Detail) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	2,443	2,779
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	22,243	20,664
4.50% Convertible Senior Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	25,000