Reinsurance - Consolidated Property Casualty Insurance Assumed and Ceded Business (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Property Casualty Insurance Assumed And Ceded Business
Earned premiums	$ 1,773	$ 1,593	$ 3,463	$ 3,137
Incurred loss and loss expenses	1,309	915	2,348	1,918
Consolidated Property And Casualty Insurance
Property Casualty Insurance Assumed And Ceded Business
Direct written premiums	1,871	1,649	3,574	3,194
Assumed written premiums	193	161	456	366
Ceded written premiums	(100)	(96)	(167)	(153)
Net written premiums	1,964	1,714	3,863	3,407
Direct earned premiums	1,631	1,465	3,192	2,894
Assumed earned premiums	134	109	255	210
Ceded earned premiums	(68)	(60)	(132)	(115)
Earned premiums	1,697	1,514	3,315	2,989
Direct incurred loss and loss expenses	1,174	781	2,069	1,649
Assumed incurred loss and loss expenses	67	54	140	132
Ceded incurred loss and loss expenses	(1)	(5)	(13)	(28)
Incurred loss and loss expenses	$ 1,240	$ 830	$ 2,196	$ 1,753