Segment Information (Details) - Assets by Segment - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Assets by segment
Total assets	$ 115,717	$ 120,466
Reportable segments [Member]
Assets by segment
Total assets	114,916	119,482
Reportable segments [Member] | Business Insurance [Member]
Assets by segment
Total assets	86,522	90,353
Reportable segments [Member] | Bond & Specialty Insurance [Member]
Assets by segment
Total assets	10,119	10,146
Reportable segments [Member] | Personal Insurance [Member]
Assets by segment
Total assets	18,275	18,983
Other assets [Member]
Assets by segment
Total assets	$ 801	$ 984