Goodwill and Other Intangible Assets (Details) - Goodwill - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Goodwill by segment
Goodwill	$ 3,976	$ 3,952
Reportable segments [Member] | Business Insurance [Member]
Goodwill by segment
Goodwill	2,585	2,565
Reportable segments [Member] | Bond & Specialty Insurance [Member]
Goodwill by segment
Goodwill	550	550
Reportable segments [Member] | Personal Insurance [Member]
Goodwill by segment
Goodwill	815	811
Other [Member]
Goodwill by segment
Goodwill	$ 26	$ 26