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Convertible Notes and Long-term Debt Obligations - Full Repayment of Department of Energy Loan Facility - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2013
DOE warrant [Member]    
Debt Instrument [Line Items]    
Other income recognized for change in fair value of warrant   $ 10.7
DOE Loan Facility [Member]    
Debt Instrument [Line Items]    
Loan facility, initiation date Jan. 20, 2010  
Debt instrument payment including principal and interest $ 451.8  
Debt instrument payment of outstanding amount 441.0  
Debt instrument penalty for early repayment 10.8  
Reserve for loan repayment $ 29.3  
Interest expense amortized during period   $ 5.8