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Segment Reporting Disclosures (Reconciliation Of Segment Assets To The Company's Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Assets	$ 55,045,710	$ 49,791,259
Investing [Member]
Segment Reporting Information [Line Items]
Assets	30,542,282	26,982,280
Underwriting Operations [Member]
Segment Reporting Information [Line Items]
Assets	9,897,689	8,853,559
Markel Ventures [Member]
Segment Reporting Information [Line Items]
Assets	5,519,542	5,315,677
Other [Member]
Segment Reporting Information [Line Items]
Assets	9,086,197	8,639,743
Segment Assets [Member]
Segment Reporting Information [Line Items]
Assets	$ 45,959,513	$ 41,151,516

X

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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