Variable Interest Entities - Schedule of Assets and Liabilities of Reciprocal Exchanges (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Investments
Fixed income securities, at fair value	$ 52,576	$ 48,865
Short-term investments	5,288	5,144
Deferred policy acquisition costs	6,112	5,940	$ 5,607
Premium installment and other receivables, net	10,762	10,044
Reinsurance recoverables, net	8,730	8,809
Other assets	6,461	6,051
Total assets	108,368	103,362
Liabilities
Reserve for property and casualty insurance claims and claims expense	41,553	39,858
Unearned premiums	25,929	24,709
Total liabilities	89,795	85,732
Variable Interest Entity, Primary Beneficiary
Investments
Fixed income securities, at fair value	227	267
Short-term investments	30	7
Deferred policy acquisition costs	17	25
Premium installment and other receivables, net	41	44
Reinsurance recoverables, net	75	76
Other assets	15	54
Total assets	405	473
Liabilities
Reserve for property and casualty insurance claims and claims expense	226	201
Unearned premiums	160	177
Other liabilities and expenses	26	77
Total liabilities	412	455
Consolidation, Eliminations
Investments
Total assets	(57)	(26)
Liabilities
Total liabilities	$ (198)	$ (189)