Property, Plant and Equipment by Classification (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Property Plant And Equipment [Line Items]
Total property, plant and equipment	$ 101,818	$ 100,034
Less accumulated depreciation and amortization	(18,114)	(16,559)
Property, plant and equipment, net	83,704	83,475
Construction in progress
Property Plant And Equipment [Line Items]
Total property, plant and equipment	67,711	66,033
Plant machinery and equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment	11,009	11,009
Property, plant and equipment, useful life	10 years
Site improvements
Property Plant And Equipment [Line Items]
Total property, plant and equipment	7,009	7,007
Property, plant and equipment, useful life	10 years
Lab equipment, furniture and fixtures and vehicles
Property Plant And Equipment [Line Items]
Total property, plant and equipment	6,369	6,303
Property, plant and equipment, useful life	5 years
Demonstration plant
Property Plant And Equipment [Line Items]
Total property, plant and equipment	3,597	3,597
Property, plant and equipment, useful life	2 years
Buildings
Property Plant And Equipment [Line Items]
Total property, plant and equipment	2,543	2,543
Property, plant and equipment, useful life	10 years
Computer, office equipment and software
Property Plant And Equipment [Line Items]
Total property, plant and equipment	1,437	1,437
Property, plant and equipment, useful life	3 years
Leasehold improvements, pilot plant, land and support equipment
Property Plant And Equipment [Line Items]
Total property, plant and equipment	$ 2,143	$ 2,105
Leasehold improvements, pilot plant, land and support equipment | Minimum
Property Plant And Equipment [Line Items]
Property, plant and equipment, useful life	2 years
Leasehold improvements, pilot plant, land and support equipment | Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, useful life	5 years