Property, Plant and Equipment by Classification (Detail) (USD $) In Thousands, unless otherwise specified					9 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended			9 Months Ended		9 Months Ended		9 Months Ended				9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Construction in progress	Dec. 31, 2013 Construction in progress	Sep. 30, 2014 Plant machinery and equipment	Dec. 31, 2013 Plant machinery and equipment	Sep. 30, 2014 Site improvements	Dec. 31, 2013 Site improvements	Sep. 30, 2014 Retrofit Asset	Sep. 30, 2014 Retrofit Asset	Sep. 30, 2014 Lab equipment, furniture and fixtures and vehicles	Dec. 31, 2013 Lab equipment, furniture and fixtures and vehicles	Sep. 30, 2014 Demonstration plant	Dec. 31, 2013 Demonstration plant	Sep. 30, 2014 Buildings	Dec. 31, 2013 Buildings	Sep. 30, 2014 Computer, office equipment and software	Dec. 31, 2013 Computer, office equipment and software	Sep. 30, 2014 Leasehold improvements, pilot plant, land and support equipment	Dec. 31, 2013 Leasehold improvements, pilot plant, land and support equipment	Sep. 30, 2014 Leasehold improvements, pilot plant, land and support equipment Minimum	Sep. 30, 2014 Leasehold improvements, pilot plant, land and support equipment Maximum
Property Plant And Equipment [Line Items]
Property, plant and equipment, useful life					10 years		10 years		20 years	20 years	5 years		2 years		10 years		3 years				2 years	5 years
Total property, plant and equipment	$ 102,234	$ 100,034	$ 356	$ 66,033	$ 13,093	$ 11,009	$ 7,009	$ 7,007	$ 65,659	$ 65,659	$ 6,369	$ 6,303	$ 3,597	$ 3,597	$ 2,543	$ 2,543	$ 1,465	$ 1,437	$ 2,143	$ 2,105
Less accumulated depreciation and amortization	(19,724)	(16,559)
Property, plant and equipment, net	$ 82,510	$ 83,475