Labor Agreements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2019 employees
Ashland Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		215
Mountain State Carbon [Member]
Concentration Risk [Line Items]
Entity Number of Employees		230
Zanesville Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		105
Butler Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		1,120
Coshocton Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		300
Middletown Works [Member]
Concentration Risk [Line Items]
Entity Number of Employees		1,715
Forecast [Member]
Concentration Risk [Line Items]
Multiemployer Plan, Contribution Increase (Decrease) | $	$ 2.0