Investments in Debt and Equity Securities - Summary of Investments In An Unrealized Loss Position That Are Not Other-Than-Temporarily Impaired (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months - Fair Value	$ 2,715	$ 177
Less than 12 months - Unrealized losses	60	0
12 months or more - Fair Value	825	763
12 months or more - Unrealized losses	52	26
Fair Value	3,540	940
Unrealized Losses	112	26
Other U.S. and non-U.S. government bonds
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months - Fair Value	0	0
Less than 12 months - Unrealized losses	0	0
12 months or more - Fair Value	29	17
12 months or more - Unrealized losses	1	0
Fair Value	29	17
Unrealized Losses	1	0
Corporate bonds and other debt securities
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months - Fair Value	2,232	130
Less than 12 months - Unrealized losses	38	0
12 months or more - Fair Value	385	306
12 months or more - Unrealized losses	15	6
Fair Value	2,617	436
Unrealized Losses	53	6
Asset-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months - Fair Value	89	38
Less than 12 months - Unrealized losses	0	0
12 months or more - Fair Value	70	43
12 months or more - Unrealized losses	1	1
Fair Value	159	81
Unrealized Losses	1	1
U.S. governmental agency
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months - Fair Value	332	3
Less than 12 months - Unrealized losses	20	0
12 months or more - Fair Value	251	307
12 months or more - Unrealized losses	29	15
Fair Value	583	310
Unrealized Losses	49	15
Residential
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months - Fair Value	0	0
Less than 12 months - Unrealized losses	0	0
12 months or more - Fair Value	4	1
12 months or more - Unrealized losses	1	1
Fair Value	4	1
Unrealized Losses	1	1
Commercial
Available-for-sale Securities, Continuous Unrealized Loss Position
Less than 12 months - Fair Value	62	6
Less than 12 months - Unrealized losses	2	0
12 months or more - Fair Value	86	89
12 months or more - Unrealized losses	5	3
Fair Value	148	95
Unrealized Losses	$ 7	$ 3

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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