Name:	met_MaximumPerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The future upper range performance factor range used to determine final number of performance shares (or units) payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

No definition available.

Name:	met_MaximumPerformanceFactorFuture
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The lower range performance factor range used to determine final number of performance shares (or units) payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

No definition available.

Name:	met_MinimumPerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The future lower range performance factor range used to determine final number of performance shares (or units) payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

No definition available.

Name:	met_MinimumPerformanceFactorFuture
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The percentage of the performance factor for the three year performance period.

No definition available.

Name:	met_PerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

As of the balance sheet date, the number of shares (or units) expected for payout based on the performance factor.

No definition available.

Name:	met_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedNumberOfSharesOrUnitsBasedOnPerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(d)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.