XML 80 R59.htm IDEA: XBRL DOCUMENT v3.24.0.1

Segment Reporting Disclosures (Narrative) (Details) - United States [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Underwriting Operations [Member]
Revenue, Major Customer [Line Items]
Percentage of gross premiums written	80.00%	80.00%	80.00%
Markel Ventures [Member]
Revenue, Major Customer [Line Items]
Percentage of revenue attributable to U.S.	95.00%	96.00%	95.00%

X

- Definition

Percentage of gross premiums written

+ References

No definition available.

+ Details

Name:	mkl_PercentageOfGrossPremiumsWritten
Namespace Prefix:	mkl_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percentage of Revenue

+ References

No definition available.

+ Details

Name:	mkl_PercentageOfRevenue
Namespace Prefix:	mkl_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

X

- 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

Name:	us-gaap_EntityWideRevenueMajorCustomerLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mkl_UnderwritingOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=mkl_MarkelVenturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: