Pension and Other Postretirement Benefits - Plan Assets Measured at Fair Value (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	$ 2,507	$ 2,363	$ 3,191
Fair Value, Recurring
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	1,739	1,600
Fair Value, Recurring | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	69	3
Fair Value, Recurring | U.S. treasury securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	107	108
Fair Value, Recurring | Government-related securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	129	133
Fair Value, Recurring | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	1,164	1,144
Fair Value, Recurring | Mortgage-backed and asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	128	101
Fair Value, Recurring | U.S. large capitalization
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	89	48
Fair Value, Recurring | U.S. small capitalization
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	18	63
Fair Value, Recurring | Exchange Trade Fund (ETF)
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	27
Fair Value, Recurring | Other
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	8
Fair Value, Recurring | Level 1
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	241	219
Fair Value, Recurring | Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0	0
Fair Value, Recurring | Level 1 | U.S. treasury securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	107	108
Fair Value, Recurring | Level 1 | Government-related securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0	0
Fair Value, Recurring | Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0	0
Fair Value, Recurring | Level 1 | Mortgage-backed and asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0	0
Fair Value, Recurring | Level 1 | U.S. large capitalization
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	89	48
Fair Value, Recurring | Level 1 | U.S. small capitalization
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	18	63
Fair Value, Recurring | Level 1 | Exchange Trade Fund (ETF)
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	27
Fair Value, Recurring | Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0
Fair Value, Recurring | Level 2
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	1,498	1,381
Fair Value, Recurring | Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	69	3
Fair Value, Recurring | Level 2 | U.S. treasury securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0	0
Fair Value, Recurring | Level 2 | Government-related securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	129	133
Fair Value, Recurring | Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	1,164	1,144
Fair Value, Recurring | Level 2 | Mortgage-backed and asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	128	101
Fair Value, Recurring | Level 2 | U.S. large capitalization
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0	0
Fair Value, Recurring | Level 2 | U.S. small capitalization
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0	0
Fair Value, Recurring | Level 2 | Exchange Trade Fund (ETF)
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	0
Fair Value, Recurring | Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	8
Fair Value, Recurring | Net Asset Value | Common collective funds
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	676	660
Fair Value, Recurring | Net Asset Value | Limited partnerships
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	10	11
Fair Value, Recurring | Net Asset Value | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Investments, at fair value	$ 82	$ 92