Schedule of Carrying Value and Fair Value by Fair Value Hierarchy of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Measurements, Recurring
Recurring:
Total Recurring Fair Value Measurements	$ 21,434	$ 28,467
Fair Value, Measurements, Recurring | Derivative Warrant Liability
Recurring:
Total Recurring Fair Value Measurements	4,942	2,698
Fair Value, Measurements, Recurring | 2017 Notes
Recurring:
Total Recurring Fair Value Measurements	16,492	25,769
Fair Value, Measurements, Nonrecurring
Nonrecurring
Total Nonrecurring Fair Value Measurements	2,092	1,327
Fair Value, Measurements, Nonrecurring | Corn and Finished Goods Inventory
Nonrecurring
Total Nonrecurring Fair Value Measurements	2,092	1,327
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Nonrecurring
Nonrecurring
Total Nonrecurring Fair Value Measurements	223	108
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Nonrecurring | Corn and Finished Goods Inventory
Nonrecurring
Total Nonrecurring Fair Value Measurements	223	108
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Recurring:
Total Recurring Fair Value Measurements		1,884
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Derivative Warrant Liability
Recurring:
Total Recurring Fair Value Measurements		1,884
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Nonrecurring
Nonrecurring
Total Nonrecurring Fair Value Measurements	1,869	1,219
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Nonrecurring | Corn and Finished Goods Inventory
Nonrecurring
Total Nonrecurring Fair Value Measurements	1,869	1,219
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Recurring:
Total Recurring Fair Value Measurements	21,434	26,583
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Derivative Warrant Liability
Recurring:
Total Recurring Fair Value Measurements	4,942	814
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | 2017 Notes
Recurring:
Total Recurring Fair Value Measurements	$ 16,492	$ 25,769