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, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning liabilities for unpaid losses and loss adjustment expenses, gross	$ 39,659
Less: payments
Ending liabilities for unpaid losses and loss adjustment expenses, gross	39,759
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	31,449	$ 29,622
Reinsurance and other recoverables	6,165	5,808	$ 6,081	$ 5,725
Beginning liabilities for unpaid losses and loss adjustment expenses, net	25,452	24,524	$ 25,368	$ 23,897
Provision for unpaid losses and loss adjustment expense
Current accident year	1,931	1,924
Prior accident year development [1]	(36)	229
Total provision for unpaid losses and loss adjustment expenses	1,895	2,153
Less: payments
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(281)	(292)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(1,525)	(1,221)
Total payments	(1,806)	(1,513)
Foreign currency adjustment	(5)	(6)
Ending liabilities for unpaid losses and loss adjustment expenses, net	25,452	24,524
Ending liabilities for unpaid losses and loss adjustment expenses, gross	31,617	30,332
Property, Liability and Casualty Insurance Product Line | Continental Europe Operations [Member]
Less: payments
Disposal Group, Including Discontinued Operation, Unpaid losses and loss adjustment expenses	0	(1)
Property, Liability and Casualty Insurance Product Line | Adverse Development Cover Navigators Group [Member]
Provision for unpaid losses and loss adjustment expense
Deferred Revenue	$ 0	$ 6