Name:	met_EstimatedFairValueCommercialMortgage
Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This represents the total estimated fair value amount for mortgage loans by credit quality indicator to the total for all mortgage loans.

No definition available.

Name:	met_EstimatedFairValueCommercialMortgagePercentage
Namespace Prefix:	met_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Reflects the percentage of the gross carrying amount of unpaid loans issued to businesses to provide financing on existing land or a building, which, pursuant to terms of the underlying debt instrument, are secured at a minimum but possibly exclusively by that real property to the total for all commercial mortgage loans. Mortgages represent permanent financing, and are issued to replace previously existing mortgages or pay off acquisition, development and construction loans, or to provide cash to the borrower.

No definition available.

Name:	met_LoansReceivableCommercialMortgagePercentage
Namespace Prefix:	met_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5066-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a)(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_LoansReceivableCommercialMortgage
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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.

No definition available.

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

Name:	us-gaap_InternalCreditAssessmentAxis=met_MortgageLoansByCreditQualityIndicatorRangeOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_InternalCreditAssessmentAxis=met_MortgageLoansByCreditQualityIndicatorRangeTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_InternalCreditAssessmentAxis=met_MortgageLoansByCreditQualityIndicatorRangeThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_InternalCreditAssessmentAxis=met_MortgageLoansByCreditQualityIndicatorRangeFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	met_DebtServiceCoverageRatioByRangeAxis=met_DebtServiceCoverageRatioRangeOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	met_DebtServiceCoverageRatioByRangeAxis=met_DebtServiceCoverageRatioRangeTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: