Reserve for Claims and Claim Expenses - Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Reserve for Claims and Claim Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	$ 15,142,583	$ 11,181,648	$ 9,025,961	$ 7,455,128
Reinsurance Recoverable	5,344,286	4,710,925	4,268,669
Total reserve for claims and claim expenses	20,486,869	$ 15,892,573	$ 13,294,630
Property
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	5,096,974
Reinsurance Recoverable	2,736,646
Casualty and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	10,045,609
Reinsurance Recoverable	$ 2,607,640