Quarterly report pursuant to Section 13 or 15(d)

Our Portfolio - Equity Method Investments, Additional Information (Details)

v3.10.0.1
Our Portfolio - Equity Method Investments, Additional Information (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
Mar. 31, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]            
Equity method investments $ 434,463,000     $ 434,463,000   $ 522,615,000
Loss from equity method investment (11,671,000)   $ (6,876,000) (19,969,000) $ (19,424,000)  
OTTI on equity method investments       0   0
Investment Contracts [Member]            
Schedule of Equity Method Investments [Line Items]            
Investment in project $ 11,000,000     $ 11,000,000    
Investment Contracts [Member] | Wind Projects [Member]            
Schedule of Equity Method Investments [Line Items]            
Equity method investments           $ 25,000,000
Loss from equity method investment   $ 8,000,000