Fair Value Measurements - Separate Accounts (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Guaranteed separate accounts	$ 555	$ 576
Non-guaranteed separate accounts	6,089	6,070
Subtotal	6,644	6,646
Non-guaranteed separate accounts priced at NAV as a practical expedient	633	632
Separate account assets	7,277	7,278
Pension Plans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-guaranteed separate accounts	3,800	3,800
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Guaranteed separate accounts	227	231
Non-guaranteed separate accounts	275	267
Subtotal	502	498
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Guaranteed separate accounts	328	345
Non-guaranteed separate accounts	5,559	5,575
Subtotal	5,887	5,920
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Guaranteed separate accounts	0	0
Non-guaranteed separate accounts	255	228
Subtotal	255	228
Significant Unobservable Inputs (Level 3) | Pension Plans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-guaranteed separate accounts	$ 200	$ 200