Securities that Potentially Dilute Calculation of Diluted Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	1,210,231	1,153,445	231,254
Warrants to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	1,103,766	1,024,635	125,212
Convertible 2017 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	75,119	75,191	75,127
2022 Notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	5,608	13,117	15,752
Outstanding options to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	16,915	24,089	12,245
Unvested restricted common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Warrants to purchase common stock	8,823	16,413	2,918