Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Percentage of annual salary Contributed by the Company for employees (401(k) plans)	4.00%
General And Administrative Expense
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost	$ 84	$ 89	$ 74
Other liabilities
Defined Benefit Plan Disclosure [Line Items]
Net accumulated liability for non-retiree postemployment benefits provided to former or inactive employee	1
Rabbi Trust
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Obligation	1,301	1,208
Fair value of plan assets	986	861
Rabbi Trust | Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Obligation	76	72
Fair value of plan assets	106	102
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Obligation	14,637	13,185	13,838
Fair value of plan assets	$ 13,906	$ 12,807	$ 13,655
Defined Benefit Plan Weighted Average Asset Allocations	100.00%	100.00%
Bond Yield rate used in determining Discount rate	3.30%	4.30%	3.65%	4.15%
Expected long-term rate of return on plan assets	6.00%	6.50%	6.25%	6.25%
Defined Benefit Plans Estimated Future Employer Contributions in Next Fiscal Year	$ 205
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Obligation	1,993	$ 1,876	$ 1,996
Fair value of plan assets	$ 1,557	$ 1,432	$ 1,615
Defined Benefit Plan Weighted Average Asset Allocations	100.00%	100.00%
Bond Yield rate used in determining Discount rate	3.25%	4.30%	3.60%	4.05%
Expected long-term rate of return on plan assets	6.75%	7.00%	7.00%	7.00%
Defined Benefit Plans Estimated Future Employer Contributions in Next Fiscal Year	$ 10
Maximum
Defined Benefit Plan Disclosure [Line Items]
Bond Yield rate used in determining Discount rate	90.00%
Maximum | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Deferred Compensation Arrangement with Individual, Requisite Age	55 years
Deferred Compensation Arrangement with Individual, Requisite Service Period	20 years
Minimum
Defined Benefit Plan Disclosure [Line Items]
Bond Yield rate used in determining Discount rate	10.00%
Minimum | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Deferred Compensation Arrangement with Individual, Requisite Age	50 years
Deferred Compensation Arrangement with Individual, Requisite Service Period	10 years
Annuity Contracts | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Obligation	$ 22	$ 18
Foreign plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Average Asset Allocations	5.00%	5.00%
Foreign plans | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension benefits for foreign plans percentage of the ending benefit obligation	14.00%	15.00%