Employee Retirement Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Credit Risk of Plan Assets, Long Duration Corporate Bonds	58.00%
Currency Fluctuations, Assets Invested in Non US Investments	12.00%
Liquidity Risk, Long Term Investments in Private Equity and Real Estate	5.00%
Defined Contribution Plan, Cost Recognized	$ 76,000,000	$ 108,000,000	$ 67,000,000
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%
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	40.00%
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Voluntary Contributions by Employer		0
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan contributions	$ 245,000,000	22,000,000
Defined Benefit Plan, Accumulated Benefit Obligation	4,700,000,000	4,300,000,000
Actuarial loss (gain)	$ 358,000,000	$ 533,000,000
Weighted average discount rate, rounded amount	0.78%	1.00%
Pension Benefits [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Voluntary Contributions by Employer	$ 180,000,000
Pension plan contributions	195,000,000	$ 14,000,000
Pension Benefits [Member] | International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Voluntary Contributions by Employer	41,000,000	2,000,000
Pension plan contributions	50,000,000	8,000,000
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	31,000,000
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan contributions	$ 60,000,000
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%
Actuarial loss (gain)	$ 58,000,000	$ 6,000,000
Weighted average discount rate, rounded amount	0.72%	0.92%
Postretirement Benefits [Member] | United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan contributions	$ 30,000,000