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Future Policy Benefits - Narrative (Details) $ in Millions | 6 Months Ended
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Jun. 30, 2024 USD ($)
Insurance [Abstract] |
Liability for Future Policy Benefit, Adverse Development, Expense, Loss At Issue | $ 126

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- Definition Amount of expense for adverse development on liability of future policy benefit from net premium exceeding gross premium for loss at issue. + References No definition available. + Details
Name: | met_LiabilityForFuturePolicyBenefitAdverseDevelopmentExpenseLossAtIssue
Namespace Prefix: | met_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_InsuranceAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration