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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Data Type:	xbrli:monetaryItemType
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- Definition

Amount of revenue and income classified as other.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.4)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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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=77990344&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

+ Details

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Balance Type:	credit
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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.

+ Details

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Variable Interest Entities (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Variable Interest Entity [Line Items]
Investment management fees earned by the Company from unconsolidated Funds	$ 330,993	$ 312,841	$ 638,909	$ 618,864
Total investment and insurance assets under management of MCIM for unconsolidated VIEs	4,400,000		4,400,000
Markel Diversified Fund [Member]
Variable Interest Entity [Line Items]
Total assets of the Markel Diversified Fund	186,000		186,000		$ 166,800
Total liabilities of the Markel Diversified Fund	63,800		63,800		64,600
Investment in one of the unconsolidated Funds	$ 183,300		$ 183,300		$ 165,100
Percentage of total assets of the Markel Diversified Fund invested in one of the unconsolidated Funds	5.00%		5.00%		6.00%
Note payable included in total liabilities of the Markel Diversified Fund delivered as part of the consideration provided for its investment	$ 62,500		$ 62,500		$ 62,500
Non-Insurance Operations [Member]
Variable Interest Entity [Line Items]
Investment management fees earned by the Company from unconsolidated Funds	328,605	310,828	631,011	610,816
Investment Management [Member] \| Non-Insurance Operations [Member]
Variable Interest Entity [Line Items]
Investment management fees earned by the Company from unconsolidated Funds	$ 9,277	$ 7,350	$ 18,636	$ 14,523