Securities that Potentially Dilute Calculation of Diluted Earnings Per Share (Detail)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	54,616,128	10,098,839
Warrants to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	22,563,548	1,259,998
Convertible 2017 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	22,537,983
Convertible 2022 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	4,725,516	4,725,392
Outstanding options to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	3,873,563	3,172,213
Unvested restricted common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	915,518	941,236