Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies- Project Assets (Details)

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Summary of Significant Accounting Policies- Project Assets (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2015
Accounting Policies [Abstract]      
Interest costs capitalized $ 164 $ 114  
Minimum qualifying operating period for prorated repayments of grants 5 years    
Deferred grant income $ 8,153   $ 8,291