Stockholders' Equity - Summary of Stock Option and Warrant Activities under Equity Incentive Plan and Warrants Issued Outside of Plan to Employees and Consultants (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options or Warrants, Balance outstanding, Beginning Balance	1,914,906	144,000
Number of Options or Warrants, Granted	5,534,692	1,812,906
Number of Options or Warrants, Cancelled (unvested)	(60,000)	(42,000)
Number of Options or Warrants, Expired (vested)	(52,000)
Number of Options or Warrants, Balance outstanding, Ending Balance	7,337,598	1,914,906	144,000
Number of Options or Warrants, Exercisable, Ending Balance	7,078,342
Weighted Average Exercise Price, Balance outstanding, Beginning Balance	$ 2.44	$ 31.74
Weighted Average Exercise Price, Granted	0.67	0.80
Weighted Average Exercise Price, Cancelled(unvested)	0.60	32.02
Weighted Average Exercise Price, Expired (vested)	28.76
Weighted Average Exercise Price, Balance outstanding, Ending Balance	0.94	$ 2.44	$ 31.74
Weighted Average Exercise Price, Exercisable, Ending Balance	$ 0.95
Weighted Average Remaining Contractual Life (in years), Balance	8 years 7 months 13 days	8 years 8 months 27 days	2 years 1 month 6 days
Weighted Average Remaining Contractual Life (in years), Granted	8 years 10 months 6 days	9 years 1 month 6 days
Weighted Average Remaining Contractual Life (in years), Exercisable, Ending Balance	8 years 7 months 6 days