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, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	$ 18,402,432	$ 16,822,101	$ 15,142,583	$ 11,181,648
Reinsurance Recoverable	3,899,913	4,481,390	5,344,286
Reserve for claims and claim expenses	22,302,345	$ 21,303,491	$ 20,486,869
Property
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	4,883,402
Reinsurance Recoverable	802,582
Casualty and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Reserve for Claims and Claim Expenses	13,519,030
Reinsurance Recoverable	$ 3,097,331

Amount, after valuation allowance, recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, policy benefits and policy reserves. Excludes premiums paid under reinsurance contracts.