Convertible Notes and Long-term Debt Obligations - DOE Warrant Expiration - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2013
Debt Instrument [Line Items]
Warrant issued to DOE, shares purchasable				3,090,111
Exercise price of the warrant issued, price per share				7.54
Fair value of warrant at issuance	$ 120,318,000
Interest expense amortized during period		600,000	600,000
Series E convertible preferred stock [Member]
Debt Instrument [Line Items]
Warrant issued to DOE, shares purchasable				9,255,035
Exercise price of the warrant issued, price per share				2.51
DOE Loan Facility [Member]
Debt Instrument [Line Items]
Fair value of warrant at issuance	6,300,000
Facility fee paid to Department of Energy	500,000
Other debt issuance costs	900,000
Interest expense amortized during period	5,800,000
DOE warrant [Member]
Debt Instrument [Line Items]
Other income recognized for change in fair value of warrant		10,700,000
Expense recognized for change in fair value of warrant		1,900,000	2,800,000
Fair value of the DOE warrant	$ 10,700,000