Commitments, Guarantees and Contingent Liabilities - California earthquake authority (Details) - California Earthquake Authority - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2022
Loss Contingencies
CEA capital balance	$ 5,600
Proceeds of revenue bonds	1,600
CEA existing reinsurance layer	9,300
Policy holder surcharge	1,000
Current estimated maximum CEA assessment	1,700
CEA capital balance threshold	350
CEA capital balance to be restored	350
Projected aggregate claim paying capacity	$ 19,100
Share of the CEA (as a percent)		8.30%
Maximum possible assessment		$ 138