v3.20.2
Equity method investments in unconsolidated affiliates - Op Results (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Operating results        
Revenue $ 62.3 $ 71.3 $ 135.0 $ 144.3
Net income (loss) (4.0) 2.9 19.7 5.3
Equity in earnings of unconsolidated affiliates 6.1 9.4 19.8 22.3
Distributions from equity method investments     (21.6) (25.4)
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]        
Operating results        
Revenue 30.5 34.6 68.3 67.4
Project expenses 24.0 24.7 47.7 44.2
Project other expenses (0.4) (0.5) (0.8) (0.9)
Equity in earnings of unconsolidated affiliates 6.1 9.4 19.8 22.3
Distributions from equity method investments (15.5) (19.6) (21.6) (25.4)
Deficit in earnings of equity method investments, net of distributions (9.4) (10.2) (1.8) (3.1)
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member] | Frederickson        
Operating results        
Revenue 6.1 10.2 14.2 16.1
Project expenses 5.0 9.0 10.5 12.4
Net income (loss) 1.1 1.2 3.7 3.7
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member] | Orlando Cogen, LP        
Operating results        
Revenue 14.6 15.3 29.1 30.7
Project expenses 6.8 7.1 13.1 14.6
Net income (loss) 7.8 8.2 16.0 16.1
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member] | Chambers Cogen, LP        
Operating results        
Revenue 9.0 9.1 19.6 20.6
Project expenses 7.9 8.6 16.0 17.2
Project other expenses (0.4) $ (0.5) (0.8) (0.9)
Net income (loss) 0.7   2.8 $ 2.5
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member] | Craven County Wood Energy, LP        
Operating results        
Revenue 0.7   3.8  
Project expenses 3.2   5.7  
Net income (loss) (2.5)   (1.9)  
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member] | Grayling Generating Station, LP        
Operating results        
Revenue 0.1   1.6  
Project expenses 1.1   2.4  
Net income (loss) $ (1.0)   $ (0.8)