Stockholders' Equity - Summary of Stock Option and Warrant Activity under 2005 Equity Incentive Plan and Warrants Issued Outside of Plan to Employees and Directors (Detail) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options or Warrants, Balance outstanding, Beginning Balance	12,116,334
Number of Options or Warrants, Balance outstanding, Ending Balance	12,116,334	12,116,334
Number of Options or Warrants, Exercisable, Ending Balance	12,110,469
Weighted Average Exercise Price, Balance outstanding, Beginning Balance	$ 0.73
Weighted Average Exercise Price, Balance outstanding, Ending Balance	0.73	$ 0.73
Weighted Average Exercise Price, Exercisable, Ending Balance	$ 0.73
Weighted Average Remaining Contractual Life (in years), Balance	7 years 4 months 13 days	7 years 8 months 2 days
Weighted Average Remaining Contractual Life (in years), Exercisable, Ending Balance	7 years 4 months 13 days