Investments (Securities Lending Remaining Tenor - Narrative) (Details) - Estimated fair value $ in Billions	Dec. 31, 2015 USD ($)
Securities Financing Transaction [Line Items]
Securities Loaned, Not Subject to Master Netting Arrangement	$ 9.9
U.S. Treasury and agency
Securities Financing Transaction [Line Items]
Percentage Of US Treasury And Agency Securities At Estimated Fair Value Of Securities On Loan Relating To Cash Collateral On Open	99.00%
Securities Investment
Securities Financing Transaction [Line Items]
Percentage of Reinvestment Portfolio in Fixed Maturity Securities	60.00%

The percentage of US Treasury and agency securities at estimated fair value of securities on loan relating to cash collateral on open.

No definition available.

+ Details

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

- Definition

The percentage of the reinvestment portfolio acquired with the cash collateral consists mainly of Fixed maturities.

+ References

No definition available.

+ Details

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

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

- Definition

Amount of securities loaned to entities in exchange for collateral, not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226052-175313

+ Details

Name:	us-gaap_SecuritiesLoanedNotSubjectToMasterNettingArrangement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_SecuritiesFinancingTransactionAxis=us-gaap_SecuritiesFinancingTransactionFairValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_SecuritiesInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: