Contingencies and Legal Matters (Details)	9 Months Ended
	Sep. 30, 2016 employee
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	189
USW | Reading, PA | September 2016 | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	29
USW | Brattleboro, VT | November 2016 | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	70
USW | Lowville, NY | November 2016 | Workforce Subject to Collective Bargaining Arrangements Expiring within One Year
Concentrations
Number of Employees	90
USW | Whiting, WI | January 2018 | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Number of Employees	204
USW | Neenah, WI | June 2018 | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Number of Employees	266
USW | Munising, MI | July 2018 | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Number of Employees	201
USW | Appleton, WI | May 2019 | Workforce Subject to Collective Bargaining Arrangements
Concentrations
Number of Employees	77
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%