v3.3.1.900
Commitments and Contingencies (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Lease expense under operating leases $ 1.5 $ 1.0 $ 1.0
Future minimum lease commitments under operating leases      
2016 0.6    
2017 0.6    
2018 0.6    
2019 0.2    
Future minimum lease commitments 2.0    
Maintenance Services for Turbine Equipment [Member]      
Long-term Purchase Commitments      
2016 0.4    
2017 0.4    
2018 0.4    
2019 0.4    
2020 0.4    
Thereafter 0.6    
Total 2.6    
Fuel and Transportation Services [Member]      
Long-term Purchase Commitments      
2016 54.0    
2017 20.8    
2018 14.4    
2019 10.4    
2020 10.4    
Thereafter 20.8    
Total $ 130.8