Unpaid Losses And Loss Adjustment Expenses (Reconciliation Of Consolidated Reserves For Losses And Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Gross reserves for losses and loss adjustment expenses, beginning of year	$ 20,947,898	$ 18,178,894	$ 16,222,376
Reinsurance recoverables on unpaid losses, beginning of year	7,994,884	6,876,317	5,736,659
Net reserves for losses and loss adjustment expenses, beginning of year	12,953,014	11,302,577	10,485,717
Effect of foreign currency rate changes on beginning of year balance	70,344	(160,622)	(54,736)
Adjusted net reserves for losses and loss adjustment expenses, beginning of year	13,023,358	11,141,955	10,430,981
Incurred losses and loss adjustment expenses, current accident year	5,360,559	4,613,035	4,061,000
Incurred losses and loss adjustment expenses, prior accident years (including deposit liability)	(38,550)	(167,446)	(478,930)
Total incurred losses and loss adjustment expenses	5,322,009	4,445,589	3,582,070
Payments, current accident year	729,895	580,537	637,169
Payments, prior accident years	2,663,165	2,396,446	2,066,290
Total payments	3,393,060	2,976,983	2,703,459
Effect of foreign currency rate changes on current year activity	(1,532)	(5,468)	(4,253)
Net reserves for losses and loss adjustment expenses of Markel CATCo Re	(162,954)	347,921	0
Liability for unpaid claims and claims adjustment expenses, business disposal	0	0	(2,762)
Reinsurance Recoverable, Retroactive Reinsurance Transaction	(125,067)	0	0
Net reserves for losses and loss adjustment expenses, end of year	14,662,754	12,953,014	11,302,577
Reinsurance recoverables on unpaid losses, end of year	8,820,567	7,994,884	6,876,317
Gross reserves for losses and loss adjustment expenses, end of year	$ 23,483,321	$ 20,947,898	$ 18,178,894

The liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims, adjusted for foreign currency movements, commutations and other events. The liability includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

No definition available.