Variable Interest Entities - Assets and liabilities of consolidated VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Investments
Fixed income securities, at fair value	$ 42,825	$ 42,565
Short-term investments, at fair value	5,516	6,807
Deferred policy acquisition costs	4,374	3,774
Premium installment receivables, net	8,146	6,463
Reinsurance and indemnification recoverables, net	9,497	7,215
Other assets, net	5,706	2,756
Total assets	132,643	125,987
Liabilities
Reserve for property and casualty insurance claims and claims expense	31,637	27,610
Unearned premiums	18,756	15,946
Total liabilities	104,451	$ 95,770
Variable Interest Entity, Primary Beneficiary
Investments
Fixed income securities, at fair value	332
Short-term investments, at fair value	23
Deferred policy acquisition costs	11
Premium installment receivables, net	44
Reinsurance and indemnification recoverables, net	99
Other assets, net	99
Total assets	608
Liabilities
Reserve for property and casualty insurance claims and claims expense	211
Unearned premiums	194
Other liabilities and expenses	226
Total liabilities	$ 631