Employee Retirement Plans (Weighted-average Assumptions Used to Determine Benefit Obligations and Net Periodic Benefit Cost) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.69%	3.41%	4.33%
Discount rate	3.41%	4.33%	3.63%
United States [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.50%	3.28%	4.28%
Rate of compensation increase	4.16%	3.50%	3.50%
Cash balance crediting rate	3.84%	3.94%	3.94%
Employee contributions crediting rate	0.62%	2.03%	3.47%
Discount rate	3.28%	4.28%	3.58%
Expected return on plan assets	6.00%	6.00%	6.00%
Rate of compensation increase	3.50%	3.50%	3.50%
Cash balance crediting rate	3.94%	3.94%	3.94%
Employee contributions crediting rate	2.03%	3.47%	2.62%
International [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.02%	1.34%	1.96%
Rate of compensation increase	3.55%	2.96%	2.96%
Cash balance crediting rate	0.94%	0.97%	0.97%
Discount rate	1.34%	1.96%	1.93%
Expected return on plan assets	1.71%	2.01%	2.13%
Rate of compensation increase	2.96%	2.96%	2.81%
Cash balance crediting rate	0.97%	0.97%	1.00%