Derivative Warrant Liability - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended								12 Months Ended
	Dec. 11, 2015	Sep. 30, 2016	Jun. 30, 2016	Apr. 30, 2016	Dec. 31, 2015	May 31, 2015	Feb. 28, 2015	Aug. 31, 2014	Dec. 31, 2013	Dec. 31, 2016	May 31, 2016	Apr. 01, 2016
Derivative [Line Items]
Additional purchase of common stock shares										4,036,683
Derivative warrant liability fair value					$ 10,493					$ 2,698
Series A
Derivative [Line Items]
Additional purchase of common stock shares							110,833			110,833
Warrant , exercise price										$ 5.80
Series B
Derivative [Line Items]
Additional purchase of common stock shares							110,833			110,833
Series C
Derivative [Line Items]
Additional purchase of common stock shares						21,500				21,500
Warrant , exercise price										$ 27.80
Series D
Derivative [Line Items]
Additional purchase of common stock shares					502,500					502,500
Warrant , exercise price										$ 2.00
Series E
Derivative [Line Items]
Additional purchase of common stock shares					400,000					400,000
Series F
Derivative [Line Items]
Additional purchase of common stock shares				514,644						514,644
Number of securities called by each warrant				1
Warrant , exercise price										$ 5.80
Series H
Derivative [Line Items]
Additional purchase of common stock shares				1,029,286						1,029,286
Number of securities called by each warrant				1
Series G
Derivative [Line Items]
Additional purchase of common stock shares				328,571						328,571
Number of securities called by each warrant				1
Series I
Derivative [Line Items]
Additional purchase of common stock shares		712,503								712,503
Number of securities called by each warrant		1
Warrant , exercise price										$ 11.00
Series J
Derivative [Line Items]
Additional purchase of common stock shares		185,000								185,000
Number of securities called by each warrant		1
375,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable											375,000
Warrant , exercise price				$ 15.00							$ 6.00
150,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable			150,000
Warrant , exercise price			$ 8.40									$ 15.00
100,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable			100,000
Warrant , exercise price			$ 10.40									$ 15.00
50,000 Exercisable Series H
Derivative [Line Items]
Shares warrants exercisable			50,000
Warrant , exercise price			$ 10.40
Series D Warrant Agreement Amendment
Derivative [Line Items]
Shares warrants exercisable			208,370
Warrant , exercise price	$ 2.00		$ 3.50
Warrants, exercise date	Jun. 11, 2016		Jun. 08, 2016
2013 Warrants
Derivative [Line Items]
Additional purchase of common stock shares									71,013	71,013
Warrant , exercise price										$ 49.80
2014 Warrants
Derivative [Line Items]
Additional purchase of common stock shares								50,000		50,000
Warrant , exercise price								$ 36.20		$ 36.20