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, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	$ 11,181,648	$ 9,025,961	$ 7,455,128	$ 6,593,052
Reinsurance Recoverable	4,710,925	4,268,669	2,926,010
Total reserve for claims and claim expenses	15,892,573	$ 13,294,630	$ 10,381,138
Property
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	4,814,431
Reinsurance Recoverable	2,721,401
Casualty and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	6,367,217
Reinsurance Recoverable	$ 1,989,524