Pension and Postretirement Benefit Plans and Defined Contribution Plans - Weighted-Average Actuarial Assumptions (Details)		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Postretirement Benefits Plan [Member]
Weighted-average assumptions used to determine benefit obligations:
Weighted-average assumptions used to determine benefit obligations, Discount rate		2.50%	3.20%	4.30%
Weighted-average assumptions used to determine net periodic benefit cost:
Weighted-average assumptions used to determine net periodic benefit cost, Discount rate		3.20%	4.30%	3.70%
Weighted-average assumptions used to determine net periodic benefit cost, Expected return on plan assets		7.00%	7.30%	7.50%
US [Member] | Pension Plan [Member] | Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations:
Weighted-average assumptions used to determine benefit obligations, Discount rate		2.60%	3.30%	4.40%
Weighted-average assumptions used to determine net periodic benefit cost:
Weighted-average assumptions used to determine net periodic benefit cost, Discount rate		3.30%	4.40%	3.80%
Weighted-average assumptions used to determine net periodic benefit cost, Expected return on plan assets		7.00%	7.20%	7.50%
Weighted-average assumptions used to determine net periodic benefit cost, Rate of compensation increase	[1]	0.00%	0.00%	2.80%
US [Member] | U.S. Supplemental (Non-Qualified) Pension Plans [Member] | Non-Qualified Plan [Member]
Weighted-average assumptions used to determine benefit obligations:
Weighted-average assumptions used to determine benefit obligations, Discount rate		2.40%	3.20%	4.30%
Weighted-average assumptions used to determine net periodic benefit cost:
Weighted-average assumptions used to determine net periodic benefit cost, Discount rate		3.20%	4.30%	3.70%
Weighted-average assumptions used to determine net periodic benefit cost, Rate of compensation increase	[1]	0.00%	0.00%	2.80%
International [Member] | Pension Plan [Member]
Weighted-average assumptions used to determine benefit obligations:
Weighted-average assumptions used to determine benefit obligations, Discount rate		1.50%	1.70%	2.50%
Weighted-average assumptions used to determine benefit obligations, Rate of compensation increase	[1]	2.90%	1.40%	1.40%
Weighted-average assumptions used to determine net periodic benefit cost:
Weighted-average assumptions used to determine interest cost, Discount rate		1.50%	2.20%	2.00%
Weighted-average assumptions used to determine service cost, Discount rate		1.60%	2.40%	2.30%
Weighted-average assumptions used to determine net periodic benefit cost, Expected return on plan assets		3.60%	3.90%	4.40%
Weighted-average assumptions used to determine net periodic benefit cost, Rate of compensation increase		2.90%	1.40%	2.50%

[1] Effective January 1, 2018, we froze the defined benefit plans to future benefit accruals in the U.S. and members’ accrued benefits to that date no longer increase in line with future compensation increases. The rate of compensation increase is therefore no longer an assumption used to determine the benefit obligation and net periodic benefit cost for the U.S. qualified and non-qualified pension plans.