Employee Retirement Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Cap on Contribution Toward Future Retiree Medical Coverage	120.00%
Percentage of Cost to Be Paid by Employees for Retiree Medical Upon Retirement	100.00%
Defined Benefit Plan, Accumulated Benefit Obligation	$ 4,300,000,000	$ 3,800,000,000
Credit Risk of Plan Assets, Long Duration Corporate Bonds	64.00%
Currency Fluctuations, Assets Invested in Non US Investments	12.00%
Liquidity Risk, Long Term Investments in Private Equity and Real Estate	7.00%
Defined Contribution Plan, Cost Recognized	$ 108,000,000	67,000,000	$ 60,000,000
Bond Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	60.00%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent to Yield	10.00%
Minimum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
Minimum [Member] | Private Equity and Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%
Minimum [Member] | Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	0.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percent to Yield	40.00%
Maximum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	25.00%
Maximum [Member] | Private Equity and Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	15.00%
Maximum [Member] | Commodities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0	105,000,000
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	85,000,000
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	2,000,000	$ 12,000,000
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	54,000,000
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)	5,000,000
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)	6,000,000
Defined Benefit Plan, Future Amortization of Gain (Loss)	$ (1,000,000)