Insurance Claim Reserves (Details) - Prior Year Reserve Development - Property-casualty [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Liability for claims and claim adjustment expense
Net favorable prior year reserve development included in estimated claims and claim adjustment expenses incurred for claims arising in prior years			$ 387	$ 459
Net favorable prior year reserve development impacting the Company's results of operations			444	499
Accretion expense			23	24
Business Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable prior year reserve development impacting the Company's results of operations	$ 202	$ 73	315	207
Bond & Specialty Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable prior year reserve development impacting the Company's results of operations	73	44	108	59
Personal Insurance [Member]
Liability for claims and claim adjustment expense
Net favorable prior year reserve development impacting the Company's results of operations	$ 16	$ 65	$ 21	$ 233