Insurance (Rollforward of Unpaid Claims) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Balance, beginning of period	$ 18,591	$ 19,216
Less: Reinsurance recoverables	2,417	2,377
Net balance, beginning of period	16,174	16,839
Incurred related to:
Current period	20,667	19,664
Prior periods (1)	960	234
Total incurred	21,627	19,898
Paid related to:
Current period	(14,426)	(13,803)
Prior periods	(6,416)	(5,378)
Total paid	(20,842)	(19,181)
Net balance, end of period	16,840	17,556
Add: Reinsurance recoverables	2,910	2,521
Balance, end of period (included in future policy benefits and other policy-related balances)	19,750	20,077
MetLife Poland and Greece
Paid related to:
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments	(55)	0
Disposal Group, Held-for-Sale or Disposed of by Sale
Paid related to:
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments	$ (64)	$ 0

The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

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Amount, after effects of reinsurance, of payments to settle claims incurred in the current period and related claims settlement costs.

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Amount, after effects of reinsurance, of payments to settle claims incurred in prior periods and related claims settlement costs.

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Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred and costs incurred in the claim settlement process.

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Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

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Sum of adjustments to the estimated reserve for unpaid claims and claims adjustment expense.

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Amount, after effects of reinsurance, of payments to settle insured claims and pay costs incurred in the claims settlement process.

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Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs.

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