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, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net earned premiums	$ 5,404	$ 5,099	$ 5,185
Loss and loss adjustment expenses	3,157	3,271	3,271
Commissions and other underwriting expenses	1,547	1,625	1,725
Net investment income	730	461	532
Net earnings, including noncontrolling interests	$ 1,995	721	869
Neon Capital Limited
Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net earned premiums		200	384
Loss and loss adjustment expenses		218	225
Commissions and other underwriting expenses		117	195
Underwriting loss		(135)	(36)
Net investment income		(5)	6
Other income and expenses, net		(5)	(10)
Net earnings, including noncontrolling interests		$ (145)	$ (40)