Employee Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2029
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate		2029
Defined Contribution Plan, Cost		$ 131	$ 120	$ 128
Scenario, Forecast
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	5.80%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed For Ultimate Fiscal Year					4.50%
U.S. Pension Plan
Derivative, Notional Amount		345	281
U.K. Pension Plan
Derivative, Notional Amount		$ 346	$ 287
Principal Plans
Defined Benefit Plan, Plan Assets, Investment Policy and Strategy, Description		there were no significant concentrations of equity or debt securities in any single issuer or industry.
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		4.59%	4.75%	4.72%
Principal Plans | Scenario, Forecast
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	3.76%
Defined Benefit Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		$ (45)	$ (136)	$ (7)
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		4.39%	4.50%	4.46%
Defined Benefit Pension Plans | Scenario, Forecast
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 50
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	3.66%
Equity Securities | Principal Plans | Scenario, Forecast
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
2018 Global Restructuring Program
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		$ (46)	$ (110)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment		$ (1)	$ (17)
Fixed Income Funds | Principal Plans | Scenario, Forecast
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	80.00%