Retirement Benefits (Schedule of Allocation of Plan Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
DB Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 3,004	$ 2,820	$ 3,599
DB Pension Plans | Plan Assets Excluding Pooled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	225	385
DB Pension Plans | Plan Assets Excluding Pooled Funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	225	385
DB Pension Plans | Plan Assets Excluding Pooled Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
DB Pension Plans | Cash and short-term investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets	178	122
DB Pension Plans | Cash and short-term investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	178	122
DB Pension Plans | Cash and short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
DB Pension Plans | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	47	263
DB Pension Plans | Mutual funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	47	263
DB Pension Plans | Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
DB Pension Plans | Pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	2,779	2,435
OPEB Plan
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1,559	1,446	$ 1,787
OPEB Plan | Plan Assets Excluding Pooled Funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	402	851
OPEB Plan | Plan Assets Excluding Pooled Funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	303	851
OPEB Plan | Plan Assets Excluding Pooled Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	99
OPEB Plan | Cash and short-term investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets	82	28
OPEB Plan | Cash and short-term investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	82	28
OPEB Plan | Cash and short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
OPEB Plan | U.S. government and agencies securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16	0
OPEB Plan | U.S. government and agencies securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
OPEB Plan | U.S. government and agencies securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16
OPEB Plan | Corporate debt
Defined Benefit Plan Disclosure [Line Items]
Plan assets	67	0
OPEB Plan | Corporate debt | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
OPEB Plan | Corporate debt | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	67
OPEB Plan | State and municipal bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1	0
OPEB Plan | State and municipal bonds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
OPEB Plan | State and municipal bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1
OPEB Plan | Foreign corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	15	0
OPEB Plan | Foreign corporate bonds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
OPEB Plan | Foreign corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	15
OPEB Plan | Common stocks
Defined Benefit Plan Disclosure [Line Items]
Plan assets	161	69
OPEB Plan | Common stocks | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	161	69
OPEB Plan | Common stocks | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
OPEB Plan | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	60	754
OPEB Plan | Mutual funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	60	754
OPEB Plan | Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
OPEB Plan | Pooled funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 1,157	$ 595