Labor Agreements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Jun. 30, 2019 employees
Ashland Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		220
Mountain State Carbon [Member]
Concentration Risk [Line Items]
Entity Number of Employees		230
Butler Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		1,200
Zanesville Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		105
Coshocton Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		305
Middletown Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		1,725
Forecast [Member]
Concentration Risk [Line Items]
Multiemployer Plan, Contribution Increase (Decrease) | $	$ 2.0