Contingencies and Legal Matters (Details)	3 Months Ended
	Mar. 31, 2018 employee
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	665
IG BCE | Germany | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Percentage of salaried employees eligible to be represented by Mining, Chemicals and Energy Trade Union (IG BCE)	50.00%
Percentage of hourly employees eligible to be represented by Mining, Chemicals and Energy Trade Union (IG BCE)	80.00%
USW | Whiting, WI | January 2018 (c) | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	198
USW | Neenah, WI | June 2018 | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	264
USW | Munising, MI | July 2018 | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	203
USW | Appleton, WI | May 2019 | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Number of Employees	105
USW | Brattleboro, VT | August 2021 | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Number of Employees	89
USW | Lowville, NY | November 2021 | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Number of Employees	107