Schedule of Shares Issued Upon Exercise of Warrants (Detail) - $ / shares	1 Months Ended							12 Months Ended
	Sep. 30, 2016	Apr. 30, 2016	Dec. 31, 2015	May 31, 2015	Feb. 28, 2015	Aug. 31, 2014	Dec. 31, 2013	Dec. 31, 2016
Derivative [Line Items]
Additional purchase of common stock shares								4,036,683
Shares Issued upon Warrant Exercises								(2,791,422)
Shares Underlying Warrants Outstanding								1,102,373
Series A
Derivative [Line Items]
Warrant, Issuance Date								Feb. 03, 2015
Warrants, Expiration date								Feb. 03, 2020
Warrant , Exercise Price								$ 5.80
Additional purchase of common stock shares					110,833			110,833
Shares Issued upon Warrant Exercises								(99,416)
Shares Underlying Warrants Outstanding								11,417
Series B
Derivative [Line Items]
Warrant, Issuance Date								Feb. 03, 2015
Warrants, Expiration date								Aug. 03, 2015
Additional purchase of common stock shares					110,833			110,833
Shares Issued upon Warrant Exercises								(96,795)
Series C
Derivative [Line Items]
Warrant, Issuance Date								May 19, 2015
Warrants, Expiration date								May 19, 2020
Warrant , Exercise Price								$ 27.80
Additional purchase of common stock shares				21,500				21,500
Shares Underlying Warrants Outstanding								21,500
Series D
Derivative [Line Items]
Warrant, Issuance Date								Dec. 11, 2015
Warrants, Expiration date								Dec. 11, 2020
Warrant , Exercise Price								$ 2.00
Additional purchase of common stock shares			502,500					502,500
Shares Issued upon Warrant Exercises								(501,570)
Shares Underlying Warrants Outstanding								930
Series E
Derivative [Line Items]
Warrant, Issuance Date								Dec. 11, 2015
Warrants, Expiration date								Dec. 11, 2020
Additional purchase of common stock shares			400,000					400,000
Shares Issued upon Warrant Exercises								(400,000)
Series F
Derivative [Line Items]
Warrant, Issuance Date								Apr. 01, 2016
Warrants, Expiration date								Apr. 01, 2021
Warrant , Exercise Price								$ 5.80
Additional purchase of common stock shares		514,644						514,644
Shares Issued upon Warrant Exercises								(233,857)
Shares Underlying Warrants Outstanding								280,787
Series G
Derivative [Line Items]
Warrant, Issuance Date								Apr. 01, 2016
Warrants, Expiration date								Apr. 01, 2017
Additional purchase of common stock shares		328,571						328,571
Shares Issued upon Warrant Exercises								(328,571)
Series H
Derivative [Line Items]
Warrant, Issuance Date								Apr. 01, 2016
Warrants, Expiration date								Oct. 01, 2016
Additional purchase of common stock shares		1,029,286						1,029,286
Shares Issued upon Warrant Exercises								(900,436)
Series I
Derivative [Line Items]
Warrant, Issuance Date								Sep. 13, 2016
Warrants, Expiration date								Sep. 13, 2021
Warrant , Exercise Price								$ 11.00
Additional purchase of common stock shares	712,503							712,503
Shares Underlying Warrants Outstanding								712,503
Series J
Derivative [Line Items]
Warrant, Issuance Date								Sep. 13, 2016
Warrants, Expiration date								Sep. 13, 2017
Additional purchase of common stock shares	185,000							185,000
Shares Issued upon Warrant Exercises								(185,000)
2013 Warrants
Derivative [Line Items]
Warrant, Issuance Date								Dec. 16, 2013
Warrants, Expiration date								Dec. 16, 2018
Warrant , Exercise Price								$ 49.80
Additional purchase of common stock shares							71,013	71,013
Shares Issued upon Warrant Exercises								(15,239)
Shares Underlying Warrants Outstanding								55,774
2014 Warrants
Derivative [Line Items]
Warrant, Issuance Date								Aug. 05, 2014
Warrants, Expiration date								Aug. 05, 2019
Warrant , Exercise Price						$ 36.20		$ 36.20
Additional purchase of common stock shares						50,000		50,000
Shares Issued upon Warrant Exercises								(30,538)
Shares Underlying Warrants Outstanding								19,462