Retirement Benefits - Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2022	Feb. 01, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Notational amount	$ 41
Net liabilities excluded	43
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	6,660	$ 8,267	$ 1,683
Derivative instruments	6
Notational amount	1,879
OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	734	$ 904	$ 0
Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	7,437
Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	6,703
Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	734
Level 1 | Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,944
Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,685
Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	259
Level 2 | Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2,012
Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,951
Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	61
Level 3 | Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	188
Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	188
Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Not subject to leveling | Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3,293
Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	2,879
Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	414
Cash equivalents | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	216
Cash equivalents | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	40
Cash equivalents | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	216
Cash equivalents | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	40
Cash equivalents | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Cash equivalents | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Cash equivalents | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Cash equivalents | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Cash equivalents | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Cash equivalents | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Equities | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,144
Equities | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	298
Equities | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	776
Equities | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	152
Equities | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Equities | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Equities | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Equities | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Equities | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	368
Equities | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	146
U.S. Treasury and agencies | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	821
U.S. Treasury and agencies | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	37
U.S. Treasury and agencies | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	693
U.S. Treasury and agencies | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	10
U.S. Treasury and agencies | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	128
U.S. Treasury and agencies | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	27
U.S. Treasury and agencies | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
U.S. Treasury and agencies | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
U.S. Treasury and agencies | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
U.S. Treasury and agencies | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
State and municipal debt | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	44
State and municipal debt | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	4
State and municipal debt | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
State and municipal debt | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
State and municipal debt | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	44
State and municipal debt | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	4
State and municipal debt | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
State and municipal debt | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
State and municipal debt | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
State and municipal debt | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Corporate debt | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	1,744
Corporate debt | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	27
Corporate debt | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Corporate debt | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Corporate debt | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	1,736
Corporate debt | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	27
Corporate debt | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	8
Corporate debt | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Corporate debt | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Corporate debt | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Other | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	513
Other | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	171
Other | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Other | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	57
Other | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	43
Other | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	3
Other | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Other | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	0
Other | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	470
Other | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Fixed income subtotal	111
Fixed income subtotal | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	3,122
Fixed income subtotal | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	239
Fixed income subtotal | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	693
Fixed income subtotal | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	67
Fixed income subtotal | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	1,951
Fixed income subtotal | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	61
Fixed income subtotal | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	8
Fixed income subtotal | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Fixed income subtotal | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	470
Fixed income subtotal | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	111
Private equity | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	765
Private equity | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private equity | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private equity | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	180
Private equity | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	585
Hedge funds | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	429
Hedge funds | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	59
Hedge funds | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Hedge funds | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Hedge funds | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Hedge funds | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Hedge funds | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Hedge funds | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Hedge funds | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	429
Hedge funds | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	59
Real estate | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	547
Real estate | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	62
Real estate | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Real estate | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Real estate | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Real estate | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Real estate | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Real estate | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Real estate | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	547
Real estate | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	62
Private credit | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	480
Private credit | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	36
Private credit | Level 1 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private credit | Level 1 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private credit | Level 2 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private credit | Level 2 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private credit | Level 3 | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private credit | Level 3 | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	0
Private credit | Not subject to leveling | Fair Value, Recurring | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	480
Private credit | Not subject to leveling | Fair Value, Recurring | OPEB
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets	$ 36