Investments - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investment [Line Items]
Mortgage loans, net	$ 784,000,000	$ 822,000,000
Fixed income securities	52,747,000,000	48,865,000,000
Short-term investments	$ 4,537,000,000	5,144,000,000
Percentage of credit concentration risk of single issuer and affiliates of shareholder's equity (as a percent)	10.00%
Fixed income and equity securities carrying value	$ 1,950,000,000	1,830,000,000
Interest income on collateral, net of fees	3,000,000	0	$ 6,000,000
Debt securities below investment grade	4,570,000,000	4,180,000,000
Fixed income and short-term investments carrying value	194,000,000
Non-income producing fixed income securities	4,000,000
Accrued investment income	615,000,000	539,000,000
Residential Mortgage
Investment [Line Items]
Mortgage loans, net	61,000,000	0
Municipal
Investment [Line Items]
Fixed income securities	8,842,000,000	6,006,000,000
Municipal bonds, tax exempt value	7,710,000,000	4,850,000,000
Fixed income securities
Investment [Line Items]
Fixed income securities	16,000,000	32,000,000
Accrued investment income	$ 574,000,000	$ 495,000,000