Reinsurance and Indemnification - Effects of reinsurance on property and casualty premiums (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property and casualty insurance premiums earned
Direct	$ 49,392	$ 45,822	$ 39,208
Assumed	252	199	113
Ceded	(1,907)	(1,982)	(1,154)
Net amount	47,737	44,039	38,167
Property and casualty insurance premiums
Property and casualty insurance premiums written
Direct	50,065	45,523	38,695
Assumed	245	213	105
Ceded	(1,824)	(1,736)	(1,142)
Property and casualty insurance premiums written, net of recoverables	48,486	44,000	37,658
Property and casualty insurance premiums earned
Direct	47,552	43,944	38,115
Assumed	221	178	99
Ceded	(1,869)	(1,904)	(1,141)
Net amount	45,904	42,218	37,073
Accident and health insurance
Property and casualty insurance premiums earned
Direct	1,622	1,722	931
Assumed	14	6	0
Ceded	(31)	(72)	(5)
Net amount	1,605	1,656	926
Accident and health insurance premiums and contract charges
Direct	1,840	1,878	1,093
Assumed	31	21	14
Ceded	(38)	(78)	(13)
Accident and health insurance premiums and contract charges, net of recoverables	$ 1,833	$ 1,821	$ 1,094