Pension and Other Postretirement 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, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 3,596	$ 5,496
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	6,473	6,525
Service cost	204	239	$ 216
Interest cost	188	184	209
Actuarial (gain) loss	(2,186)	(188)
Benefits paid	(464)	(263)
Curtailment	0	(12)
Other	(34)	(12)
Projected benefit obligation at end of year	4,181	6,473	6,525
Change in plan assets:
Fair value of plan assets at beginning of year	4,626	4,069
Actual income (loss) on plan assets	(678)	437
Employer contributions	8	387
Benefits paid	(464)	(263)
Other	(25)	(4)
Fair value of plan assets at end of year	3,467	4,626	4,069
Funded status—Net amount recognized	(714)	(1,847)
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent asset	44	75
Current liability	(11)	(2)
Noncurrent liability	(747)	(1,920)
Total liability	(714)	(1,847)
Amounts recognized in accumulated other comprehensive income ( loss) consist of:
Net actuarial loss	(77)	(1,406)
Prior service cost	(1)	(1)
Total accumulated other comprehensive loss	(78)	(1,407)
Other Postretirement Benefits
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	1,129	1,082
Service cost	9	10	10
Interest cost	30	25	28
Plan participants' contributions	69	66
Actuarial (gain) loss	(270)	114
Benefits paid	(179)	(199)
Special termination benefit	0	31
Projected benefit obligation at end of year	788	1,129	1,082
Change in plan assets:
Fair value of plan assets at beginning of year	49	51
Actual income (loss) on plan assets	1	1
Employer contributions	108	130
Plan participants' contributions	69	66
Benefits paid	(179)	(199)
Fair value of plan assets at end of year	48	49	$ 51
Funded status—Net amount recognized	(740)	(1,080)
Amounts recognized in the consolidated balance sheets consist of:
Current liability	(69)	(80)
Noncurrent liability	(671)	(1,000)
Total liability	(740)	(1,080)
Amounts recognized in accumulated other comprehensive income ( loss) consist of:
Net actuarial loss	369	113
Prior service cost	335	447
Total accumulated other comprehensive loss	$ 704	$ 560