Pension Plans and Other Postretirement Benefits - Benefit Obligations and Plan Assets (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in benefit obligation:
Benefit obligation, beginning of year	$ 6,462	$ 6,239
Interest cost	110	168	$ 225
Actuarial (gain) loss	(102)	413
Benefit payments	(408)	(358)
Settlements	(53)	0
Benefit obligation, end of year	6,009	6,462	6,239
Change in plan assets:
Beginning balance	6,845	6,395
Actual return on plan assets	215	783
Employer contributions	78	25	25
Benefit payments	(408)	(358)
Settlements	(53)	0
Ending balance	6,677	6,845	$ 6,395
Funded status	668	383
Assets (liabilities) recognized on the consolidated balance sheet
Noncurrent assets reflected in other assets	946	744
Current liabilities reflected in accrued expenses	(28)	(76)
Noncurrent liabilities reflected in other long-term liabilities	(250)	(285)
Net assets	$ 668	$ 383

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.