Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Income tax expense (benefit)	$ 354	$ 138	$ 550
Legal entity merger tax impact	(147)	0	0
Tax Cuts and Jobs Act of 2017, incomplete accounting, provisional income tax expense			49
Tax Cuts and Jobs Act of 2017, incomplete accounting, transition tax for accumulated foreign earnings, provisional income tax expense			190
Effective income tax rate reconciliation, Tax Cuts and Jobs Act, additional income tax benefit		54
Pension plan contributions, tax deductible		350
Effective income tax rate reconciliation, Tax Cuts and Jobs Act, additional income tax expense		95
Effective income tax rate reconciliation, Tax Cuts and Jobs Act, unrecognized tax benefits	117	55
U.S. transition tax expense recognized to date		26
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Income Tax Expense	299
Transition tax provision, deemed remittance		3,500
Cash and cash equivalents as presented in our Consolidated Balance Sheets	1,952	1,498	1,196
Operating loss carryforwards	5,600
Operating loss carryforwards, not subject to expiration	3,300
U.S. general business credit carryforwards, including Energy Tax Credits	787	875
Valuation allowance, deferred tax assets	192	348
Valuation allowance, increase in deferred tax assets		150
Unrecognized tax benefits, income tax penalties and interest expense (benefit)	(4)	2	8
Unrecognized tax benefits, income tax penalties and interest accrued	42	46	$ 45
Unrecognized tax benefits	4
United States Pension Benefits
Cash and Cash Equivalents [Line Items]
Operating loss carryforwards	695
Net Operating Loss Carryforward
Cash and Cash Equivalents [Line Items]
Valuation allowance, deferred tax assets	111	286
Other Deferred Tax Assets
Cash and Cash Equivalents [Line Items]
Valuation allowance, deferred tax assets	$ 81	$ 62