Fair Value Measurements - Changes in Unrealized Gains (Losses) Included in Net Income for Financial Instruments Classified as Level 3 Still Held at Year End (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses)	Net realized gains (losses)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	$ (8)	$ (25)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	(1)	2
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Other Comprehensive Income (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	74	(199)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Other Comprehensive Income (Loss) [Member] | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	(6)	(3)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | CLO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	(6)	(3)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | Residential mortgage-backed securities ("RMBS")
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | Other Comprehensive Income (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	74	(199)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | Other Comprehensive Income (Loss) [Member] | CLO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	1	(1)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | Other Comprehensive Income (Loss) [Member] | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	2	(15)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | Other Comprehensive Income (Loss) [Member] | Corporate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	71	(170)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Securities available-for-sale and other | Total fixed maturities | Other Comprehensive Income (Loss) [Member] | Residential mortgage-backed securities ("RMBS")
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	0	(13)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Fair Value Option, Other Eligible Items | Total fixed maturities | CLO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	(1)	(24)
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring [Member] | Fair Value Option, Other Eligible Items | Total fixed maturities | Other Comprehensive Income (Loss) [Member] | CLO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in Unrealized Gain/(Loss) Included in Net Income, Assets	$ 0	$ 0