Assumed variable annuity guarantee reserves

No definition available.

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Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Reserves for Group Annuity products

+ References

No definition available.

+ Details

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Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount awarded to other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

+ Details

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

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the maximum amount of estimated loss and the amount recorded as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 05
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6395354&loc=d3e12631-108344

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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Namespace Prefix:
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- Details

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- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_AsbestosIssueMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_EnvironmentalRemediationSiteAxis=met_SuperfundSiteSettlementAgreementsMember
Namespace Prefix:
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Contingencies, Commitments and Guarantees (Contingencies - Narrative) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) Claims	Mar. 31, 2017 Claims	Dec. 31, 2017 USD ($) Claims
Loss Contingencies
Reserves for Group Annuity products			$ 510,000
Assumed variable annuity guarantee reserves			$ 896,000
Minimum
Loss Contingencies
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 0
Maximum
Loss Contingencies
Loss Contingency, Range of Possible Loss, Portion Not Accrued	$ 700,000
Asbestos Related Claims
Loss Contingencies
Asbestos-Related Claims \| Claims	823	1,104	3,514
Superfund Site Settlement Agreements
Loss Contingencies
Number of regulatory matters and other claims \| Claims	2
Superfund Site Settlement Agreements \| Maximum
Loss Contingencies
Maximum estimate of aggregate costs to resolve matter	$ 300