Aggregate number of shares owed under stock option plans and other equity-based compensation arrangements.

No definition available.

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of the performance factor for the future three year performance period used for performance shares and units.

+ References

No definition available.

+ Details

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Namespace Prefix:	met_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of the performance factor for the three year performance period used for performance shares and units.

+ References

No definition available.

+ Details

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Namespace Prefix:	met_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

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

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

- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

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

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=met_OtherStockAndIncentivePlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=met_TwoThousandFifteenDirectorStockPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=met_OtherDirectorStockPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=met_LiabilityAwardsPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_RangeAxis=srt_MinimumMember
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Equity (Stock-Based Compensation Plans - Narrative) (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
2015 Stock Plan
Equity - Stock-based Compensation Plans [Line Items]
Aggregate number of shares authorized for issuance		31,886,521
Other Stock And Incentive Plans
Equity - Stock-based Compensation Plans [Line Items]
Deferred shares		686,770
2015 Director Stock Plan
Equity - Stock-based Compensation Plans [Line Items]
Aggregate number of shares authorized for issuance		1,469,329
Other Director Stock Plans
Equity - Stock-based Compensation Plans [Line Items]
Deferred shares		323,898
Stock Options
Equity - Stock-based Compensation Plans [Line Items]
Award Expiration Date		10 years	10 years	10 years
Stock Options \| Maximum
Equity - Stock-based Compensation Plans [Line Items]
Vesting period		3 years
Stock Options \| Liability Awards Plan
Equity - Stock-based Compensation Plans [Line Items]
Paid		0
Performance Shares
Equity - Stock-based Compensation Plans [Line Items]
Paid		(1,489,328)
Performance Factor			141.30%
Performance Shares \| Scenario, Forecast
Equity - Stock-based Compensation Plans [Line Items]
Paid	(1,174,602)
Performance Shares \| Minimum
Equity - Stock-based Compensation Plans [Line Items]
Future Performance Factor		0.00%
Performance Shares \| Maximum
Equity - Stock-based Compensation Plans [Line Items]
Future Performance Factor		175.00%
Performance Shares \| Liability Awards Plan
Equity - Stock-based Compensation Plans [Line Items]
Paid		(156,900)
Performance Shares \| Liability Awards Plan \| Scenario, Forecast
Equity - Stock-based Compensation Plans [Line Items]
Paid	(154,904)