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Basis of Presentation - Additional Information (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Variable Interest Entity [Line Items]        
Foreign currency translation adjustment $ 56,179 $ 47,712 $ 199,303 $ 95,425
Windfield Holdings        
Variable Interest Entity [Line Items]        
Foreign currency translation adjustment   $ 12,500