Reserve for Unpaid Losses and Loss Adjustment Expenses - P&C Liabilities for Unpaid Losses and Loss Adjustment Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning liabilities for unpaid losses and loss adjustment expenses, gross	$ 41,243
Less: payments
Ending liabilities for unpaid losses and loss adjustment expenses, gross	41,582
Property, Liability and Casualty Insurance Product Line
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning liabilities for unpaid losses and loss adjustment expenses, gross	33,083	$ 31,449
Reinsurance and other recoverables	6,469	6,165	$ 6,465	$ 6,081
Beginning liabilities for unpaid losses and loss adjustment expenses, net	26,929	25,452	$ 26,618	$ 25,368
Provision for unpaid losses and loss adjustment expense
Current accident year	2,270	1,931
Prior accident year development	0	(36)
Total provision for unpaid losses and loss adjustment expenses	2,270	1,895
Less: payments
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(321)	(281)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(1,646)	(1,525)
Total payments	(1,967)	(1,806)
Foreign currency adjustment	8	(5)
Ending liabilities for unpaid losses and loss adjustment expenses, net	26,929	25,452
Ending liabilities for unpaid losses and loss adjustment expenses, gross	$ 33,398	$ 31,617