Benefit Plans - Pension Plan Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Limited Partnership Investments [Abstract]
Percentage of carrying value of investments in private debt and equity	99.00%	93.00%
Percentage of carrying value of investments employing hedge fund strategies	1.00%	7.00%
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	$ 0	$ 0
Hedge Funds, Equity Related
Limited Partnership Investments [Abstract]
Percentage of carrying value of investments in limited partnerships	100.00%
Hedge Funds, Multi-Strategy Approach Hedge Funds
Limited Partnership Investments [Abstract]
Percentage of carrying value of investments in limited partnerships	0.00%
Hedge Funds, Distressed Investments
Limited Partnership Investments [Abstract]
Percentage of carrying value of investments in limited partnerships	0.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	$ 1,004	2,074	$ 2,212
Pension Benefits | Total
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	700	1,664
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	143	304
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	544	1,346
Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	13	14
Pension Benefits | Total fixed maturities
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	540	1,353
Pension Benefits | Total fixed maturities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0	10
Pension Benefits | Total fixed maturities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	527	1,329
Pension Benefits | Total fixed maturities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	13	14
Pension Benefits | Corporate bonds and other
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	413	1,057
Pension Benefits | Corporate bonds and other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets		10
Pension Benefits | Corporate bonds and other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	408	1,041
Pension Benefits | Corporate bonds and other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	5	6
Pension Benefits | States, municipalities and political subdivisions
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	6	55
Pension Benefits | States, municipalities and political subdivisions | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | States, municipalities and political subdivisions | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	6	55
Pension Benefits | States, municipalities and political subdivisions | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	121	241
Pension Benefits | Asset-backed | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Asset-backed | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	113	233
Pension Benefits | Asset-backed | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	8	8
Pension Benefits | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	59	160
Pension Benefits | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	44	154
Pension Benefits | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	15	6
Pension Benefits | Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	59	114
Pension Benefits | Short-term investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	59	114
Pension Benefits | Short-term investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Short-term investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Fixed income mutual funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	40	26
Pension Benefits | Fixed income mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	40	26
Pension Benefits | Fixed income mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Fixed income mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Other assets
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	2	11
Pension Benefits | Other assets | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Other assets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	2	11
Pension Benefits | Other assets | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets
Pension Benefits | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total plan assets		$ 25
Defined Benefit Plan, Plan Assets, Fair Value by Hierarchy and NAV [Extensible Enumeration]		Fair Value Measured at Net Asset Value Per Share [Member]
Pension Benefits | Limited partnerships
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	$ 304	$ 385
Defined Benefit Plan, Plan Assets, Fair Value by Hierarchy and NAV [Extensible Enumeration]	Fair Value Measured at Net Asset Value Per Share [Member]	Fair Value Measured at Net Asset Value Per Share [Member]