Variable Interest Entities (Narrative) (Details) $ in Millions	Jun. 30, 2016 USD ($)
Variable Interest Entity [Line Items]
Total investment and insurance assets under management of MCIM for unconsolidated VIEs	$ 3,400.0
Other Fund [Member]
Variable Interest Entity [Line Items]
Investment in one of the unconsolidated Funds	25.2
Markel Diversified Fund [Member]
Variable Interest Entity [Line Items]
Total assets of the Markel Diversified Fund	161.8
Total liabilities of the Markel Diversified Fund	63.9
Investment in one of the unconsolidated Funds	$ 158.3
Percentage of total assets of the Markel Diversified Fund invested in one of the unconsolidated Funds	6.00%
Note payable included in total liabilities of the Markel Diversified Fund delivered as part of the consideration provided for its investment	$ 62.5

Total investment and insurance assets under management related to unconsolidated variable interest entities.

No definition available.

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- Definition

The Company's investment in one of the unconsolidated Funds.

+ References

No definition available.

+ Details

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- Definition

Percentage of the outstanding preference shares of the investment in one of the unconsolidated Funds.

+ References

No definition available.

+ Details

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- Definition

Note payable delivered as part of the consideration provided for its investment.

+ References

No definition available.

+ Details

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- Definition

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5710-111685

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- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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