Nature of Operations (Details)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Oct. 01, 2016
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
agreement
Sep. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Liquidity                
Net loss attributable to common shareholders   $ 13,420 $ 10,238 $ 38,354 $ 30,568 $ 55,800 $ 88,600 $ 62,800
Accumulated deficit   1,032,230   1,032,230   993,876    
Net cash used in operating activities       29,669 37,296      
Net loss attributable to the Company   (13,394) (10,213) (38,276) (30,490)      
Noncash gains       4,800        
Net inflows of noncash operating assets and liabilities       3,800        
Cash and cash equivalents   42,486 $ 85,009 42,486 $ 85,009 63,961 $ 146,205  
Net working capital   50,400   50,400   88,500    
Cash added to the restricted accounts   0   $ 0   $ 14,200    
Number of power purchase agreements | agreement       7        
Remaining lease payment   54,395   $ 54,395        
Purchases of property, plant, and equipement and cash outflows associated with construction of leased assets       45,100        
Subsequent event                
Liquidity                
Cash added to the restricted accounts $ 12,000              
Power purchase agreements                
Liquidity                
Remaining lease payment   $ 22,300   22,300        
Master Lease                
Liquidity                
Minimum level of unrestricted cash       $ 40,000        
Number of years that the underlying assets not be deployed       5 years        
Residual exposure       $ 12,000        
Secured term loan facility                
Liquidity                
Prior to net income milestones met, required minimum cash and cash equivalents percent of outstanding principal amount       75.00%        
Accounts payable days outstanding threshold       150 days