Investments - Net Investment Income (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) Investment	Dec. 31, 2024 USD ($) Investment	Dec. 31, 2023 USD ($)
Net Investment Income [Line Items]
Investment income, operating	$ 2,881	$ 2,877	$ 2,489
Investment expenses	(102)	(97)	(94)
Net investment income	2,779	2,780	2,395
Net investment income recognized due to the change in fair value of equity and trading portfolio securities held	$ 63	$ 93	38
Number of investments in single issuer exceeding 10% | Investment	0	0
Fixed maturity securities
Net Investment Income [Line Items]
Investment income, operating	$ 2,140	$ 2,050	1,941
Limited partnership investments
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	278	271	177
Short-term investments
Net Investment Income [Line Items]
Investment income, operating	76	90	78
Equity securities
Net Investment Income [Line Items]
Investment income, operating	60	82	63
Income from trading portfolio
Net Investment Income [Line Items]
Investment income, operating	209	255	125
Other
Net Investment Income [Line Items]
Investment income, operating	$ 118	$ 129	$ 105