XML 61 R49.htm IDEA: XBRL DOCUMENT v3.21.2
Derivative Instruments (Details)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2021
USD ($)
Jun. 30, 2021
USD ($)
BTU
Dec. 31, 2020
USD ($)
BTU
Derivative [Line Items]      
Gain (loss) on derivatives $ (3.3) $ (2.8)  
Natural Gas | Commodity Contract | Not Designated as Hedging Instrument      
Derivative [Line Items]      
Derivative energy measure (in BTUs) | BTU   4,000 0
Natural gas swap contracts, current asset     $ 0.0
Natural gas swap contracts, current liability $ 2.5 $ 2.5 $ 0.0