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, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Analysis of changes in the liability for losses and loss adjustment expenses, net of reinsurance
Balance at beginning of period	$ 10,392	$ 10,232	$ 9,741
Less reinsurance recoverables, net of allowance	3,419	3,117	3,024	$ 2,942
Net liability at beginning of period	7,275	7,208	6,799
Liability for losses and loss adjustment expenses, period increase (decrease) [Abstract]
Provision for losses and LAE occurring in the current year	3,436	3,398	3,414
Net increase (decrease) in the provision for claims of prior years:
Total losses and LAE incurred	3,157	3,271	3,271
Payments for losses and LAE of:
Current year	(1,024)	(990)	(1,076)
Prior years	(1,753)	(1,766)	(1,790)
Total payments	(2,777)	(2,756)	(2,866)
Reserves of businesses disposed	0	(449)	0
Foreign currency translation and other	0	1	4
Net liability at end of period	7,655	7,275	7,208
Add back reinsurance recoverables, net of allowance	3,419	3,117	3,024
Gross unpaid losses and LAE included in the balance sheet	11,074	10,392	10,232
Special A&E charges
Net increase (decrease) in the provision for claims of prior years:
Special A&E charges	0	47	18
Neon exited lines
Net increase (decrease) in the provision for claims of prior years:
Prior year claims and claims adjustment expense	0	19	7
Other
Net increase (decrease) in the provision for claims of prior years:
Prior year claims and claims adjustment expense	$ (279)	$ (193)	$ (168)