Schedule of Shares Issued Upon Exercise of Warrants (Detail) - $ / shares	1 Months Ended						6 Months Ended
	Apr. 30, 2016	Dec. 31, 2015	May 31, 2015	Feb. 28, 2015	Aug. 31, 2014	Dec. 31, 2013	Jun. 30, 2016
Derivative [Line Items]
Additional purchase of common stock shares							62,783,587
Shares Issued upon Warrant Exercises							(47,426,026)
Shares Underlying Warrants Outstanding							15,076,495
Series A
Derivative [Line Items]
Warrant, Issuance Date							Feb. 03, 2015
Warrants, Expiration date							Feb. 03, 2020
Warrant , Exercise Price							$ 0.30
Additional purchase of common stock shares				2,216,667			2,216,667
Shares Issued upon Warrant Exercises							(1,988,335)
Shares Underlying Warrants Outstanding							228,332
Series B
Derivative [Line Items]
Warrant, Issuance Date							Feb. 03, 2015
Warrants, Expiration date							Aug. 03, 2015
Warrant , Exercise Price							$ 0.01
Additional purchase of common stock shares				2,216,667			2,216,667
Shares Issued upon Warrant Exercises							(1,935,601)
Series C
Derivative [Line Items]
Warrant, Issuance Date							May 19, 2015
Warrants, Expiration date							May 19, 2020
Warrant , Exercise Price							$ 1.84
Additional purchase of common stock shares			430,000				430,000
Shares Underlying Warrants Outstanding							430,000
Series D
Derivative [Line Items]
Warrant, Issuance Date							Dec. 11, 2015
Warrants, Expiration date							Dec. 11, 2020
Warrant , Exercise Price							$ 0.10
Additional purchase of common stock shares		10,050,000					10,050,000
Shares Issued upon Warrant Exercises							(10,006,400)
Shares Underlying Warrants Outstanding							43,600
Series E
Derivative [Line Items]
Warrant, Issuance Date							Dec. 11, 2015
Warrants, Expiration date							Dec. 11, 2016
Warrant , Exercise Price							$ 0.01
Additional purchase of common stock shares		8,000,000					8,000,000
Shares Issued upon Warrant Exercises							(8,000,000)
Series F
Derivative [Line Items]
Warrant, Issuance Date							Apr. 01, 2016
Warrants, Expiration date							Apr. 01, 2021
Warrant , Exercise Price							$ 0.30
Additional purchase of common stock shares	10,292,858						10,292,858
Shares Underlying Warrants Outstanding							10,292,858
Series G
Derivative [Line Items]
Warrant, Issuance Date							Apr. 01, 2016
Warrants, Expiration date							Apr. 01, 2017
Warrant , Exercise Price							$ 0.01
Additional purchase of common stock shares	6,571,429						6,571,429
Shares Issued upon Warrant Exercises							(6,571,429)
Series H
Derivative [Line Items]
Warrant, Issuance Date							Apr. 01, 2016
Warrants, Expiration date							Oct. 01, 2016
Warrant , Exercise Price							$ 0.75
Additional purchase of common stock shares	20,585,716						20,585,716
Shares Issued upon Warrant Exercises							(18,008,716)
Shares Underlying Warrants Outstanding							2,577,000
2013 Warrants
Derivative [Line Items]
Warrant, Issuance Date							Dec. 16, 2013
Warrants, Expiration date							Dec. 16, 2018
Warrant , Exercise Price							$ 3.57
Additional purchase of common stock shares						1,420,250	1,420,250
Shares Issued upon Warrant Exercises							(304,774)
Shares Underlying Warrants Outstanding							1,115,476
2014 Warrants
Derivative [Line Items]
Warrant, Issuance Date							Aug. 05, 2014
Warrants, Expiration date							Aug. 05, 2019
Warrant , Exercise Price							$ 2.51
Additional purchase of common stock shares					1,000,000		1,000,000
Shares Issued upon Warrant Exercises							(610,771)
Shares Underlying Warrants Outstanding							389,229