Variable Interest Entities - Assets and liabilities of consolidated VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments
Fixed income securities	$ 42,136	$ 42,565
Short-term investments	4,009	6,807
Deferred policy acquisition costs	4,722	3,774	$ 3,600	$ 3,457
Premium installment receivables, net	8,364	6,463
Reinsurance and indemnification recoverables, net	10,024	7,215
Other assets, net	6,086	2,756
Total assets	99,440	125,987
Liabilities
Reserve for property and casualty insurance claims and claims expense	33,060	27,610
Unearned premiums	19,844	15,946
Other liabilities and accrued expenses	9,296	7,840
Total liabilities	74,313	$ 95,770
Variable Interest Entity, Primary Beneficiary
Investments
Fixed income securities	324
Short-term investments	30
Deferred policy acquisition costs	15
Premium installment receivables, net	42
Reinsurance and indemnification recoverables, net	114
Other assets, net	82
Total assets	607
Liabilities
Reserve for property and casualty insurance claims and claims expense	226
Unearned premiums	175
Other liabilities and accrued expenses	265
Total liabilities	$ 666