Securities that Potentially Dilute Calculation of Diluted Earnings Per Share (Detail)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	69,578,417	10,191,334
Warrants to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	37,563,548	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	3,741,150	3,172,213
Unvested restricted common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	1,010,220	1,033,731