Schedule VI - Supplementary Information For Property and Casualty Insurance Underwriters (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Net Losses and Loss Adjustment Expenses Incurred Related to Current Year	$ 6,784	$ 5,797	$ 4,940
Net Losses and Loss Adjustment Expenses Incurred Related to Prior Years	(538)	(769)	(355)
Consolidated Subsidiaries
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Deferred Acquisition Costs	1,531	1,263	901
Reserves for Losses and Loss Adjustment Expenses	22,752	20,032	17,758
Discount, if any, deducted in Column C	66	61	56
Unearned Premiums	8,808	7,337	6,012
Net Premiums Earned	12,440	9,679	8,082
Net investment income	1,023	496	389
Net Losses and Loss Adjustment Expenses Incurred Related to Current Year	6,784	5,797	4,940
Net Losses and Loss Adjustment Expenses Incurred Related to Prior Years	(538)	(769)	(355)
Amortization of Deferred Acquisition Costs	2,312	1,740	1,303
Net Paid Losses and Loss Adjustment Expenses	4,093	3,141	2,827
Net Premiums Written	$ 13,468	$ 11,078	$ 9,017