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Amount of amortization expected to be recognized during the fifth fiscal year following the latest fiscal year for liabilities lacking physical substance with a finite life.

No definition available.

Name:	met_FiniteLivedIntangibleLiabilitiesAmortizationYearFive
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Amount of amortization expected to be recognized during the fourth fiscal year following the latest fiscal year for liabilities lacking physical substance with a finite life.

No definition available.

Name:	met_FiniteLivedIntangibleLiabilitiesAmortizationYearFour
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Period Type:	instant

Amount of amortization expected to be recognized during the third fiscal year following the latest fiscal year for liabilities lacking physical substance with a finite life.

No definition available.

Name:	met_FiniteLivedIntangibleLiabilitiesAmortizationYearThree
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Period Type:	instant

Amount of amortization expected to be recognized during the second fiscal year following the latest fiscal year for liabilities lacking physical substance with a finite life.

No definition available.

Name:	met_FiniteLivedIntangibleLiabilitiesAmortizationYearTwo
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Negative value of business acquired.

No definition available.

Name:	met_NegativeValueOfBusinessAcquiredAbstract
Namespace Prefix:	met_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	us-gaap_ExpectedAmortizationExpenseOfEndingPresentValueOfFutureInsuranceProfitsNetOfInterestAccruedAbstract
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Expected amortization expense in the fifth year after the balance sheet date of the present value of the future profits of long-duration contracts acquired in a purchase of an insurance enterprise.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section S99
-Paragraph 2
-Subparagraph (3)
-URI http://asc.fasb.org/extlink&oid=27015749&loc=d3e569990-122904

Name:	us-gaap_ExpectedAmortizationExpenseOfEndingPresentValueOfFutureInsuranceProfitsYearFive
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Expected amortization expense in the fourth year after the balance sheet date of the present value of the future profits of long-duration contracts acquired in a purchase of an insurance enterprise.

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Expected amortization expense in the first year after the balance sheet date of the present value of the future profits of long-duration contracts acquired in a purchase of an insurance enterprise.

Name:	us-gaap_ExpectedAmortizationExpenseOfEndingPresentValueOfFutureInsuranceProfitsYearOne
Namespace Prefix:	us-gaap_
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Expected amortization expense in the third year after the balance sheet date of the present value of the future profits of long-duration contracts acquired in a purchase of an insurance enterprise.

Name:	us-gaap_ExpectedAmortizationExpenseOfEndingPresentValueOfFutureInsuranceProfitsYearThree
Namespace Prefix:	us-gaap_
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Expected amortization expense in the second year after the balance sheet date of the present value of the future profits of long-duration contracts acquired in a purchase of an insurance enterprise.

Name:	us-gaap_ExpectedAmortizationExpenseOfEndingPresentValueOfFutureInsuranceProfitsYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Name:	us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths
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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

Name:	us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo
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- References

No definition available.