Employee Retirement Plans (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
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	$ 3,800	$ 3,900
Credit Risk of Plan Assets, Long Duration Corporate Bonds	59.00%
Currency Fluctuations, Assets Invested in Non US Investments	12.00%
Liquidity Risk, Long Term Investments in Private Equity and Real Estate	8.00%
Defined Contribution Plan, Cost Recognized	$ 67	60	$ 53
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]
Number of Bonds | item	350
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]
Number of Bonds | item	375
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	$ 105
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	75
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	12
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	31
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)	7
Pension Benefits [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount		0
Pension Benefits [Member] | International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount		$ 29
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)	7
Defined Benefit Plan, Future Amortization of Gain (Loss)	$ 1