Fair Value Measurements - Additional Information (Detail) - USD ($)	1 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2016	Apr. 30, 2016	Dec. 31, 2015	May 31, 2015	Feb. 28, 2015	Aug. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2013	Sep. 13, 2016	Apr. 01, 2016	Dec. 11, 2015	May 19, 2015	Feb. 03, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of principal amount			$ 21,565,000
Derivative warrant liability fair value	$ 10,723,000		10,493,000				$ 10,723,000
Series A Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock shares issued and sold					2,216,667
Series B Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock shares issued and sold					2,216,667
Series C Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock shares issued and sold				430,000
Warrants Issued in 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock shares issued and sold									1,420,250
Warrants Issued In Two Thousand And Fourteen
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common stock shares issued and sold						1,000,000
Series D Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	10,000		$ 10,000				10,000					$ 5,700,000
Common Stock Units Issued			10,050,000
Series E Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common Stock Units Issued			8,000,000
Series F Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	4,600,000						4,600,000
Common Stock Units Issued		10,292,858
Series G Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	0						0
Common Stock Units Issued		6,571,429
Series H Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	0						0
Common Stock Units Issued		20,585,716
Series I Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	$ 5,600,000						5,600,000
Common Stock Units Issued	14,250,000
Series J Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	$ 0						0
Common Stock Units Issued	3,700,000
2017 Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of principal amount	$ 25,194,000		$ 21,565,000				25,194,000
Fair Value, Inputs, Level 2 | 2017 Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of principal amount	25,200,000		21,600,000				25,200,000
Fair Value, Inputs, Level 2 | 2022 Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of principal amount	8,800,000		14,300,000				8,800,000
Estimated fair value of the embedded derivatives	0		0				0
Fair Value, Inputs, Level 3 | Series A Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	100,000		900,000				100,000							$ 1,400,000
Fair Value, Inputs, Level 3 | Series B Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value														$ 2,500,000
Fair Value, Inputs, Level 3 | Series C Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	100,000		100,000				100,000						$ 1,200,000
Fair Value, Inputs, Level 3 | Warrants Issued in 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	200,000		200,000				200,000
Fair Value, Inputs, Level 3 | Warrants Issued In Two Thousand And Fourteen
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value	$ 100,000		100,000				100,000
Fair Value, Inputs, Level 3 | Series F Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value											$ 2,200,000
Fair Value, Inputs, Level 3 | Series H Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value											2,100,000
Fair Value, Inputs, Level 3 | Series I Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value										$ 5,700,000
Fair Value, Inputs, Level 1 | Series E Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value			$ 4,000,000									$ 5,300,000
Fair Value, Inputs, Level 1 | Series G Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value											$ 1,600,000
Fair Value, Inputs, Level 1 | Series J Warrant
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative warrant liability fair value										$ 1,800,000
Corn
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Write down of inventory							$ 0	$ 100,000