Variable Interest Entities - Schedule of Assets and Liabilities of Reciprocal Exchanges (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Assets
Fixed income securities, at fair value	$ 57,186	$ 52,747
Short-term investments	8,743	4,537
Premium installment and other receivables, net	11,745	10,614
Reinsurance recoverables, net	9,519	8,924
Other assets	5,448	5,140
Total assets	120,402	111,617
Liabilities
Reserve for property and casualty insurance claims and claims expense	43,103	41,917
Unearned premiums	29,157	26,909
Total liabilities	92,913	90,250
Variable Interest Entity, Primary Beneficiary
Assets
Fixed income securities, at fair value	3	47
Short-term investments	74	112
Premium installment and other receivables, net	0	9
Reinsurance recoverables, net	32	76
Other assets	0	25
Total assets	109	269
Liabilities
Reserve for property and casualty insurance claims and claims expense	131	214
Unearned premiums	0	22
Other liabilities and expenses	187	235
Total liabilities	$ 318	$ 471