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

Investment disclosure of credit risk exposure amount to fixed maturity securities in single issuer other than securities of the U.S. government, certain U.S. government agencies and certain securities guaranteed by the U.S. government, as well as securities of the Mexican government and certain Mexican government agencies greater than a stated percentage of Company's stockholders' equity.

No definition available.

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

Investment disclosure of credit risk exposure to fixed maturity securities in single issuer greater than a stated percentage of Company's stockholders' equity.

No definition available.

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

Investment disclosure of credit risk exposure to fixed maturity securities in single issuer lesser than a stated percentage of Company's stockholders' equity.

No definition available.

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

Disclosure of exposure amount in equity securities holdings of a single issuer greater than a stated percentage.

No definition available.

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

Investment disclosure of credit risk exposure to equity securities holdings greater than a stated percentage of the Company's stockholders' equity.

No definition available.

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

Investment disclosure of holdings in sovereign fixed maturity securities of Portugal, Ireland, Italy, Greece and Spain, commonly referred to as Europe's perimeter region, stated at estimated fair value.

No definition available.

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

This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties. This is not greater than 10% of the Company's Equity.

No definition available.

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

Investment disclosure of Net exposure in holdings in sovereign fixed maturity securities of Portugal, Ireland, Italy, Greece and Spain, commonly referred to as Europe's perimeter region, stated percentage of total cash and invested assets.

No definition available.

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

No definition available.

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

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

No definition available.