v3.2.0.727

Other Revenues And Other Expenses (Narrative) (Details) $ in Millions	Apr. 24, 2015 USD ($)
Other Income and Expenses [Abstract]
Cash payments for life and annuity benefit policies transferred under novated reinsurance contract	$ 29.0
Reserves on novated life and annuity benefit reinsurance contract	32.6
Gain on novated life and annuity benefit reinsurance contract	$ 3.6

X

- Definition

The total gain recorded as an offset to other expenses for life and annuity benefits on the novated reinsurance contract.

+ References

No definition available.

+ Details

Name:	mkl_GainOnNovatedReinsuranceContract
Namespace Prefix:	mkl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

The total amount of reserves for life and annuity benefits on the novated reinsurance contract.

+ References

No definition available.

+ Details

Name:	mkl_ReservesOnNovatedLifeAndAnnuityBenefitReinsuranceContract
Namespace Prefix:	mkl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The total cash payment, net of commissions for life and annuity benefit policies whose obligations were transferred under a novated reinsurance contract to a third party.

+ References

No definition available.

+ Details

Name:	mkl_TotalCashPaymentsForLifeAndAnnuityTransferObligation
Namespace Prefix:	mkl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- References

No definition available.

+ Details

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