Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Project Assets and Asset Retirement Obligations (Details)

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Summary of Significant Accounting Policies - Project Assets and Asset Retirement Obligations (Details) - USD ($)
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2016
Accounting Policies [Abstract]      
Interest costs capitalized $ 1,159,000 $ 164,000  
Property, Plant and Equipment [Line Items]      
Capital lease assets, net $ 4,452,000   $ 5,018,000
Minimum qualifying operating period for prorated repayments of grants 5 years    
Deferred grant income $ 7,602,000   7,739,000
Asset retirement obligation     0
Assets Held under Capital Leases      
Property, Plant and Equipment [Line Items]      
Capital lease assets 20,534,000   15,640,000
Less - accumulated depreciation and amortization (963,000)   (744,000)
Capital lease assets, net $ 19,571,000   $ 14,896,000