Variable Interest Entities - Assets and liabilities of consolidated VIEs (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investments
Fixed income securities, at fair value	$ 40,594	$ 42,565
Short-term investments, at fair value	6,017	6,807
Total	60,076	59,540
Cash	709	311
Premium installment receivables, net	7,921	6,463
Reinsurance and indemnification recoverables, net	9,645	7,215
Other assets, net	5,803	2,756
Total assets	129,811	125,987
Liabilities
Reserve for property and casualty insurance claims and claims expense	31,414	27,610
Unearned premiums	18,177	15,946
Total liabilities	103,019	$ 95,770
Variable Interest Entity, Primary Beneficiary
Investments
Fixed income securities, at fair value	281
Short-term investments, at fair value	61
Total	342
Cash	8
Premium installment receivables, net	43
Reinsurance and indemnification recoverables, net	112
Other assets, net	109
Total assets	614
Liabilities
Reserve for property and casualty insurance claims and claims expense	223
Unearned premiums	189
Other liabilities and expenses	229
Total liabilities	$ 641