Investments - Narrative (Details)	12 Months Ended
	Dec. 31, 2025 USD ($) investment	Dec. 31, 2024 USD ($) investment	Dec. 31, 2023 USD ($)	Jan. 01, 2025 USD ($)	Aug. 06, 2024 USD ($)
Net Investment Income [Line Items]
Allowance for credit losses	$ 21,000,000	$ 6,000,000
Other noncurrent assets	2,310,000,000	2,140,000,000
Net investment income	$ 2,194,000,000	$ 2,051,000,000	$ 1,825,000,000
Number of fixed maturity investments that did not produce income | investment	10	9
Assets held by insurance regulators	$ 1,121,000,000	$ 1,035,000,000
Accrued investment income receivable	295,000,000	287,000,000
Securities loaned, fair value of collateral	$ 2,691,000,000	$ 2,305,000,000
Securities lending transactions ratio of fair value of collateral held to fair value of securities loaned	102.00%	102.00%
Operating expense	$ 20,984,000,000	$ 20,025,000,000	20,087,000,000
Fixed maturity securities
Net Investment Income [Line Items]
Proceeds from sale of available-for-sale securities	11,609,000,000	16,334,000,000	$ 12,289,000,000
Third party investments
Net Investment Income [Line Items]
Contractual obligation	1,542,000,000	1,442,000,000
Rated notes
Net Investment Income [Line Items]
Contractual obligation	321,000,000	423,000,000
Cash | Overnight and Continuous
Net Investment Income [Line Items]
Collateral received for securities loaned, at carrying value	2,136,000,000	2,115,000,000
United States Government securities | Overnight and Continuous
Net Investment Income [Line Items]
Collateral received for securities loaned, at carrying value	552,000,000	176,000,000
Residential mortgage-backed securities | Overnight and Continuous
Net Investment Income [Line Items]
Collateral received for securities loaned, at carrying value	3,000,000	14,000,000
Liberty Dental
Net Investment Income [Line Items]
Operating expense	583,000,000	519,000,000
Mosaic Health
Net Investment Income [Line Items]
Operating expense	732,000,000
Mosaic Health
Net Investment Income [Line Items]
Commitment to fund	70,000,000
Subsidiary Credit Facilities | Mosaic Health
Net Investment Income [Line Items]
Line of credit facility, maximum borrowing capacity	282,000,000	188,000,000			$ 200,000,000
Subsidiary Credit Facilities | Mosaic Health | Equity Method Investee
Net Investment Income [Line Items]
Net investment income	18,000,000	7,000,000
Revolving Credit Facility | Mosaic Health
Net Investment Income [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000				500,000,000
Mosaic Health
Net Investment Income [Line Items]
Interest ownership	40.00%
Equity method investments					$ 2,580,000,000
Additional equity method investment amount				$ 300,000,000
Additional ownership percentage				0.05
Liberty Dental
Net Investment Income [Line Items]
Interest ownership	40.00%
Redeemable preferred equity shares value		250,000,000
Redeemable preferred equity shares disbursed	$ 165,000,000	87,000,000
Mandatorily redeemable preferred equity	$ 137,000,000	$ 87,000,000