Retirement Plans (Fair Value of Plan Assets By Investment Category Within The Fair Value Hierarchy - Pension Benefits) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure Line Items
Maximum equity holding percentage of total fair value		1.00%	1.00%
Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		$ 15,167	$ 14,751	$ 13,177
Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		777	705	644
Fair Value | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		14,237	14,040
Fair Value | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		767	697
Fair Value | Cash and equivalents | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		130	112
Fair Value | Cash and equivalents | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		12	16
Fair Value | Equity securities | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		105	97
Fair Value | U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	1,143	1,137
Fair Value | Non-U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	151	90
Fair Value | Private equity investments | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]		33
Fair Value | Fixed-income securities | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		154	134
Fair Value | Corporate bonds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[2]	4,090	3,532
Fair Value | Treasury securities | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		1,495	1,129
Fair Value | Equity funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		6,592	7,306
Fair Value | Equity funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		354	320
Fair Value | Fixed-income funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		430	416
Fair Value | Fixed-income funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		140	128
Fair Value | Real estate funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		8	90
Fair Value | Real estate funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		2	2
Fair Value | Insurance deposit contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		163	157
Fair Value | Retirement annuity contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		35	38
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		1,303	1,227
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		107	99
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and equivalents | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		9	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and equivalents | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		105	97
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	1,143	1,137
Quoted Prices in Active Markets for Identical Assets (Level 1) | Non-U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	151	90
Quoted Prices in Active Markets for Identical Assets (Level 1) | Private equity investments | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed-income securities | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[2]	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Treasury securities | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed-income funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed-income funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Real estate funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Real estate funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		2	2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Insurance deposit contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Retirement annuity contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Other Observable Inputs (Level 2) | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		12,728	12,495
Significant Other Observable Inputs (Level 2) | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		660	598
Significant Other Observable Inputs (Level 2) | Cash and equivalents | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		121	112
Significant Other Observable Inputs (Level 2) | Cash and equivalents | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		12	16
Significant Other Observable Inputs (Level 2) | Equity securities | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Other Observable Inputs (Level 2) | U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	0	0
Significant Other Observable Inputs (Level 2) | Non-U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	0	0
Significant Other Observable Inputs (Level 2) | Private equity investments | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]		0
Significant Other Observable Inputs (Level 2) | Fixed-income securities | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		154	134
Significant Other Observable Inputs (Level 2) | Corporate bonds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		4,090	3,532
Significant Other Observable Inputs (Level 2) | Treasury securities | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		1,495	1,129
Significant Other Observable Inputs (Level 2) | Equity funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		6,592	7,306
Significant Other Observable Inputs (Level 2) | Equity funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		354	320
Significant Other Observable Inputs (Level 2) | Fixed-income funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		430	416
Significant Other Observable Inputs (Level 2) | Fixed-income funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		140	128
Significant Other Observable Inputs (Level 2) | Real estate funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Other Observable Inputs (Level 2) | Real estate funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Other Observable Inputs (Level 2) | Insurance deposit contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Other Observable Inputs (Level 2) | Retirement annuity contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Unobservable Inputs (Level 3)
Compensation And Retirement Disclosure Line Items
Total pension plan assets		206	318	282
Significant Unobservable Inputs (Level 3) | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		206	318
Significant Unobservable Inputs (Level 3) | Cash and equivalents | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Unobservable Inputs (Level 3) | U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	0	0
Significant Unobservable Inputs (Level 3) | Non-U.S. companies | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]	0	0
Significant Unobservable Inputs (Level 3) | Private equity investments
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	33	26
Significant Unobservable Inputs (Level 3) | Private equity investments | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[1]		33
Significant Unobservable Inputs (Level 3) | Corporate bonds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[2]	0	0
Significant Unobservable Inputs (Level 3) | Treasury securities | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Unobservable Inputs (Level 3) | Equity funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Unobservable Inputs (Level 3) | Fixed-income funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		0	0
Significant Unobservable Inputs (Level 3) | Real estate funds
Compensation And Retirement Disclosure Line Items
Total pension plan assets		8	90	84
Significant Unobservable Inputs (Level 3) | Real estate funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		8	90
Significant Unobservable Inputs (Level 3) | Insurance deposit contracts
Compensation And Retirement Disclosure Line Items
Total pension plan assets		163	157	137
Significant Unobservable Inputs (Level 3) | Insurance deposit contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		163	157
Significant Unobservable Inputs (Level 3) | Retirement annuity contracts
Compensation And Retirement Disclosure Line Items
Total pension plan assets		35	38	$ 35
Significant Unobservable Inputs (Level 3) | Retirement annuity contracts | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets		35	38
Plan assets measured using NAV as a practical expedient | Equity funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[3]	38	11
Plan assets measured using NAV as a practical expedient | Real estate funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[3]	632	446
Plan assets measured using NAV as a practical expedient | Real estate funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[4]	7	5
Plan assets measured using NAV as a practical expedient | Hedge funds | Pension Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[3]	260	254
Plan assets measured using NAV as a practical expedient | Hedge funds | Other  Post-retirement Benefits
Compensation And Retirement Disclosure Line Items
Total pension plan assets	[4]	$ 3	$ 3

[1] No single equity holding amounted to more than 1% of the total fair value.

[2] Our corporate bond investments had an average rating of A-.

[3] Investments measured at fair value using NAV as a practical expedient are not classified in the fair value hierarchy. The fair value amounts presented in this table for these investments are included to permit reconciliation of the fair value hierarchy to the total plan assets.

[4] Investments measured at fair value using NAV as a practical expedient are not classified in the fair value hierarchy. The fair value amounts presented in this table for these investments are included to permit reconciliation of the fair value hierarchy to the total plan assets.