Pension Plans and Other Postretirement Benefits - Benefit Obligations and Plan Assets (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in benefit obligation:
Benefit obligation, beginning of year	$ 4,740	$ 6,009
Interest cost	231	132	$ 110
Actuarial loss (gain)	145	(1,011)
Benefit payments	(380)	(387)
Settlements	0	(3)
Benefit obligation, end of year	4,736	4,740	6,009
Change in plan assets:
Beginning balance	5,346	6,677
Actual return on plan assets	389	(968)
Employer contributions	24	27	78
Benefit payments	(380)	(387)
Settlements	0	(3)
Ending balance	5,379	5,346	$ 6,677
Funded status	643	606
Assets (liabilities) recognized on the consolidated balance sheet
Noncurrent assets reflected in other assets	856	827
Current liabilities reflected in accrued expenses	(24)	(24)
Noncurrent liabilities reflected in other long-term liabilities	(189)	(197)
Net assets	$ 643	$ 606

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

Name:	us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1