Insurance - Reinsurance information table including assumed, ceded, and recoveries (Details) - Property and casualty insurance - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effects of Reinsurance [Line Items]
Direct premiums written	$ 7,700	$ 6,862	$ 7,044
Reinsurance assumed	246	225	255
Reinsurance ceded	(2,373)	(2,074)	(1,957)
Net written premiums	5,573	5,013	5,342
Direct premiums earned	7,462	6,846	6,848
Reinsurance assumed	249	237	226
Reinsurance ceded	(2,307)	(1,984)	(1,889)
Net earned premiums	5,404	5,099	5,185
Reinsurance recoveries	$ 1,478	$ 1,522	$ 1,404