XML 59 R48.htm IDEA: XBRL DOCUMENT v3.24.2

Products, Services and Other Revenues (Schedule Of Revenues From Disposition of Business) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2023 USD ($)
ISIC [Member]
Schedule of Business Dispositions, by Dispositions [Line Items]
Gain on sale of business	$ 16,900

X

- Definition

Schedule of Business Dispositions, by Dispositions [Line Items]

+ References

No definition available.

+ Details

Name:	mkl_ScheduleOfBusinessDispositionsByDispositionsLineItems
Namespace Prefix:	mkl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481203/810-10-50-1B

+ Details

Name:	us-gaap_GainLossOnSaleOfBusiness
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	mkl_BusinessDispositionAxis=mkl_ISICMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: