Pension, Postretirement And Other Employee Benefit Plans - Reconciliation of the Change in Benefit Obligation and Plan Asset, Funded Status and Amounts Recognized in the Financial Statements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 3,910	$ 3,596
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	4,181	6,473
Service cost	124	204	$ 239
Interest cost	217	188	184
Actuarial (gain) loss	204	(2,186)
Benefits paid	(177)	(464)
Other	1	(34)
Projected benefit obligation at end of year	4,550	4,181	6,473
Change in plan assets:
Fair value of plan assets at beginning of year	3,467	4,626
Actual income (loss) on plan assets	281	(678)
Employer contributions	22	8
Benefits paid	(177)	(464)
Other	6	(25)
Fair value of plan assets at end of year	3,599	3,467	4,626
Funded status—Net amount recognized	(951)	(714)
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent asset	21	44
Current liability	(4)	(11)
Noncurrent liability	(968)	(747)
Total liability	(951)	(714)
Amounts recognized in accumulated other comprehensive income (loss) consist of:
Net actuarial loss	(242)	(77)
Prior service cost	0	(1)
Total accumulated other comprehensive loss	(242)	(78)
Other Postretirement Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	788	1,129
Service cost	4	9	10
Interest cost	42	30	25
Plan participants' contributions	67	69
Actuarial (gain) loss	22	(270)
Benefits paid	(177)	(179)
Projected benefit obligation at end of year	746	788	1,129
Change in plan assets:
Fair value of plan assets at beginning of year	48	49
Actual income (loss) on plan assets	1	1
Employer contributions	107	108
Plan participants' contributions	67	69
Benefits paid	(177)	(179)
Fair value of plan assets at end of year	46	48	$ 49
Funded status—Net amount recognized	(700)	(740)
Amounts recognized in the consolidated balance sheets consist of:
Current liability	(63)	(69)
Noncurrent liability	(637)	(671)
Total liability	(700)	(740)
Amounts recognized in accumulated other comprehensive income (loss) consist of:
Net actuarial loss	309	369
Prior service cost	222	335
Total accumulated other comprehensive loss	$ 531	$ 704