Other Postretirement Benefits - Schedule of Fair Values of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 524	$ 459
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	929	860	$ 1,150	$ 1,115
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	717	649
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	331	339
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	323	285
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	25	25
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Asset Allocation Funds
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	38
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	148	139
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Investments, Including Funds For Retiree Health Benefit
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	865	788
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Funds For Retiree Health Benefits Measured At Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	45	51
Other Postretirement Benefits | Fair Value, Inputs, Level 1 and 2 | Pending Activities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	19	21
Other Postretirement Benefits | Level 1 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	7	10
Other Postretirement Benefits | Level 1 | Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	0
Other Postretirement Benefits | Level 1 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0	10
Other Postretirement Benefits | Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	7	0
Other Postretirement Benefits | Level 1 | Asset Allocation Funds
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	0
Other Postretirement Benefits | Level 1 | Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	52	48
Other Postretirement Benefits | Level 1 | Investments, Including Funds For Retiree Health Benefit
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	59	58
Other Postretirement Benefits | Level 2 | Total investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	710	639
Other Postretirement Benefits | Level 2 | Equity
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	331	339
Other Postretirement Benefits | Level 2 | Other Fixed Income Debt
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	323	275
Other Postretirement Benefits | Level 2 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	18	25
Other Postretirement Benefits | Level 2 | Asset Allocation Funds
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	38
Other Postretirement Benefits | Level 2 | Funds For Retiree Health Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	96	91
Other Postretirement Benefits | Level 2 | Investments, Including Funds For Retiree Health Benefit
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan net assets	$ 806	$ 730