Insurance - Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance
Balance at beginning of period	$ 11,974	$ 11,074	$ 10,392
Less reinsurance recoverables, net of allowance	4,288	3,767	3,419	$ 3,117
Net liability at beginning of period	8,207	7,655	7,275
Provision for losses and LAE occurring in the current year	4,256	3,914	3,436
Net increase (decrease) in the provision for claims of prior years:
Total losses and LAE incurred	4,033	3,629	3,157
Payments for losses and LAE of:
Current year	(1,261)	(1,212)	(1,024)
Prior years	(2,181)	(1,870)	(1,753)
Total payments	(3,442)	(3,082)	(2,777)
Foreign currency translation and other	1	5	0
Net liability at end of period	8,799	8,207	7,655
Add back reinsurance recoverables, net of allowance	4,288	3,767	3,419
Gross unpaid losses and LAE included in the balance sheet	13,087	11,974	11,074
Net decrease in the provision for claims of prior years
Net increase (decrease) in the provision for claims of prior years:
Prior year claims and claims adjustment expense	$ (223)	$ (285)	$ (279)