Reserve for Unpaid Losses and Loss Adjustment Expenses - PC Additional Information (Details) - USD ($) $ in Millions		9 Months Ended
	Apr. 20, 2023	Sep. 30, 2023	Dec. 31, 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Liability for Claims and Claims Adjustment Expense		$ 41,686	$ 41,243
Reinsurance Recoverables, Gross		7,072	$ 7,069
Abuse Claims | General Liability [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Liability for Claims and Claims Adjustment Expense		787
Prior accident years	$ 787
Reinsurance Contract [Axis]: Asbestos and Environmental | Asbestos and Environmental
Liability for Claims and Claims Adjustment Expense [Line Items]
Change in Deferred Gain on Retroactive Reinsurance		594
Maximum | Reinsurance Contract [Axis]: Asbestos and Environmental | Asbestos and Environmental
Liability for Claims and Claims Adjustment Expense [Line Items]
Reinsurance, Excess Retention, Amount Reinsured, Per Policy		$ 1,500