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 $)
3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Dec. 31, 2013
Accounting Policies [Abstract]          
Interest costs capitalized $ 0 $ 596,000 $ 395,000 $ 1,311,000  
Minimum qualifying operating period for prorated repayments of grants     5 years    
Amounts received from grants     3,727,000 1,580,000  
Deferred grant income $ 8,980,000   $ 8,980,000   $ 8,163,000