(Fair Values Pension Plan Assets By Asset Class) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 12,018	$ 10,165	$ 8,735
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	3,770	2,900
Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	5,765	5,074
Significant Unobservable Inputs (Level 3) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	8	(5)	111
Equities – domestic
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,806	1,613
Equities – domestic | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,037	965
Equities – domestic | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	769	648
Equities – domestic | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	0
Equities – international
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,921	2,181
Equities – international | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,181	1,599
Equities – international | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	740	582
Equities – international | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	0
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,345	1,845
Corporate bonds | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	2,345	1,845
Government securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	3,377	2,659
Government securities | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	3,377	2,659
Mortgage backed securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	133	1
Mortgage backed securities | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	133	1
Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	(1,585)	(647)
Other fixed income | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	(1,599)	(661)
Other fixed income | Significant Unobservable Inputs (Level 3) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	14	14	13
Derivatives
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	336	(19)
Derivatives | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	342
Derivatives | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount		0
Derivatives | Significant Unobservable Inputs (Level 3) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	(6)	(19)	$ 98
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	210	336
Cash and cash equivalents | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	210	336
Cash and cash equivalents | Significant Observable Inputs (Level 2) [Member] | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount		0
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	1,112	902
Private equity
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	563	522
Real estate funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 800	$ 772