Insurance - Reinsurance information table including assumed, ceded, and recoveries (Details) - Property and casualty insurance - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Effects of Reinsurance [Line Items]
Direct premiums written	$ 8,774	$ 7,700	$ 6,862
Reinsurance assumed	283	246	225
Reinsurance ceded	(2,851)	(2,373)	(2,074)
Net written premiums	6,206	5,573	5,013
Direct premiums earned	8,582	7,462	6,846
Reinsurance assumed	274	249	237
Reinsurance ceded	(2,771)	(2,307)	(1,984)
Net earned premiums	6,085	5,404	5,099
Reinsurance recoveries	$ 2,065	$ 1,478	$ 1,522