Retirement Benefits - Assumptions (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement benefits other than pension
Defined Benefit Plan Disclosure [Line Items]
Pension cost	2.40%	3.30%	4.40%
Benefit obligation at year end	2.90%	2.40%	3.30%
Expected return on assets	8.00%	8.00%	8.00%
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Pension cost	2.40%	3.30%	4.40%
Benefit obligation at year end	2.80%	2.40%	3.30%
Expected return on assets	7.00%	7.00%	7.00%
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Pension cost	2.30%	3.20%	4.00%
Benefit obligation at year end	2.80%	2.30%	3.20%
Expected return on assets	3.55%	3.28%	5.64%
Average rate of increase in salaries - pension cost	1.90%	2.60%	2.60%
Average rate of increase in salaries - benefit obligation at year end	1.60%	1.90%	2.60%
UMWA Plans
Defined Benefit Plan Disclosure [Line Items]
Pension cost	2.30%	3.20%	4.30%
Benefit obligation at year end	2.80%	2.30%	3.20%
Black Lung and Other Plans
Defined Benefit Plan Disclosure [Line Items]
Pension cost	2.20%	3.10%	4.20%
Benefit obligation at year end	2.70%	2.20%	3.10%