Insurance - Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance
Balance at beginning of year	$ 11,974	$ 11,074
Less reinsurance recoverables, net of allowance	3,767	3,419
Net liability at beginning of year	8,207	7,655
Provision for losses and LAE occurring in the current period	3,132	2,869
Net decrease in the provision for claims of prior years	(168)	(226)
Total losses and LAE incurred	2,964	2,643
Payments for losses and LAE of:
Current year	(743)	(667)
Prior years	(1,745)	(1,501)
Total payments	(2,488)	(2,168)
Foreign currency translation and other	1	1
Net liability at end of period	8,684	8,131
Add back reinsurance recoverables, net of allowance	4,207	3,936
Gross unpaid losses and LAE included in the balance sheet at end of period	$ 12,891	$ 12,067