Segment Reporting Disclosures (Narrative) (Details) $ in Thousands	6 Months Ended
Jun. 30, 2025 USD ($) segment	Dec. 31, 2024 USD ($)
Segment Reporting Information [Line Items]
Goodwill	$ 2,826,530	$ 2,735,867
Number of Reportable Segments \| segment	3
Markel Insurance
Segment Reporting Information [Line Items]
Goodwill	$ 1,000,000
Goodwill, Impairment Loss	0
Other Insurance Operations [Member]
Segment Reporting Information [Line Items]
Goodwill	490,300
Goodwill, Impairment Loss	$ 0

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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+ Details

- Definition

Amount of impairment loss from asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

+ References + Details