Acquisitions - Initial Accounting for the 2015 Acquisitions (Details)
$ in Millions
 3 Months Ended
Oct. 07, 2015
USD ($)
power_plant
MW
Sep. 18, 2015
USD ($)
wind_project
MW
Dec. 31, 2015
USD ($)
Jun. 09, 2015
MW
May 14, 2015
wind_project
MW
Honiton          
Business Acquisition [Line Items]          
Provisional adjustment increase (decrease) to power plants     $ (0.4)    
Provisional adjustment increase (decrease) to accrued expenses and other liabilities     (0.4)    
Number of projects acquired | wind_project         3
Capacity of power plant | MW         148.5
NSM 24          
Business Acquisition [Line Items]          
Provisional adjustment increase (decrease) to power plants     (18.0)    
Provisional adjustment increase (decrease) to cash and cash equivalent     2.1    
Provisional adjustment increase (decrease) to restricted cash     (2.1)    
Provisional adjustment increase (decrease) to accounts receivable     0.5    
Provisional adjustment increase (decrease) to intangibles     17.8    
Provisional adjustment increase (decrease) to deferred tax liabilities     (0.1)    
Provisional adjustment Increase (decrease) to long-term debt     0.5    
Capacity of power plant | MW       24.0  
Witkop / Soutpan          
Business Acquisition [Line Items]          
Provisional adjustment increase (decrease) to power plants     (1.4)    
Provisional adjustment increase (decrease) to accrued expenses and other liabilities     (2.3)    
Provisional adjustment increase (decrease) to cash and cash equivalent     (0.1)    
Provisional adjustment increase (decrease) to restricted cash     0.6    
Provisional adjustment increase (decrease) to intangibles     (18.1)    
Provisional adjustment increase (decrease) to deferred tax liabilities     (2.9)    
Provisional adjustment Increase (decrease) to long-term debt     (8.9)    
Provisional adjustment increase (decrease) to other assets     (0.3)    
Provisional adjustment increase (decrease) to non-controlling interest     (5.4)    
Renova (Salvador / Bahia)          
Business Acquisition [Line Items]          
Provisional adjustment increase (decrease) to power plants     (2.7)    
Provisional adjustment increase (decrease) to accrued expenses and other liabilities     (0.9)    
Provisional adjustment increase (decrease) to cash and cash equivalent     (4.0)    
Provisional adjustment increase (decrease) to restricted cash     0.1    
Provisional adjustment increase (decrease) to accounts receivable     (3.5)    
Provisional adjustment Increase (decrease) to long-term debt     (0.4)    
Provisional adjustment increase (decrease) to other assets     $ 8.7    
Number of projects acquired | wind_project   2      
Capacity of power plant | MW   306.7      
Acquisition purchase price   $ 321.3      
FERSA          
Business Acquisition [Line Items]          
Number of projects acquired | power_plant 3        
Capacity of power plant | MW 101.6        
Acquisition purchase price $ 72.4        
Amount paid to repurchase debt $ 39.0