Acquisitions and Sale of Businesses - Revenues, costs and expenses, and earnings before income taxes of business disposed (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net earned premiums	$ 6,085	$ 5,404	$ 5,099
Loss and loss adjustment expenses	3,629	3,157	3,271
Commissions and other underwriting expenses	1,718	1,547	1,625
Net investment income	717	730	461
Net earnings, including noncontrolling interests	$ 898	$ 1,995	721
Neon Capital Limited
Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net earned premiums			200
Loss and loss adjustment expenses			218
Commissions and other underwriting expenses			117
Underwriting loss			(135)
Net investment income			(5)
Other income and expenses, net			(5)
Net earnings, including noncontrolling interests			$ (145)