Fair Value (Details 4) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Commercial mortgage loans and securities classified as trading securities the related long-term debt carried under fair value option
Mortgage Loans on Real Estate, Commercial and Consumer, Net	$ 60,819	$ 58,976
Variable interest entities
Commercial mortgage loans and securities classified as trading securities the related long-term debt carried under fair value option
Mortgage Loans on Real Estate, Commercial and Consumer, Net	6,697	6,840
Commercial mortgage loans held by consolidated securitization entities [Member]
Commercial mortgage loans and securities classified as trading securities the related long-term debt carried under fair value option
Unpaid principal balance	6,468	6,636
Excess estimated fair value over unpaid principle balance	$ 229	$ 204

Commercial Mortgage Loans And Securities Classified As Trading Securities The Related Long-Term Debt Carried Under Fair Value Option.

Name:	met_CommercialMortgageLoansAndSecuritiesClassifiedAsTradingSecuritiesRelatedLongTermDebtCarriedUnderFairValueOptionAbstract
Namespace Prefix:	met
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This caption presents the unpaid principal balance of mortgage loans held by securitization entities for which the Company has determined that it is the primary beneficiary of the variable interest entity requiring consolidation.

+ Details

Name:	met_MortgageLoansHeldByConsolidatedSecuritizationEntitiesCarriedUnderFairValueOption
Namespace Prefix:	met
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of loans and long-term receivables (other than securities categorized as trading, available-for-sale or held-to-maturity) that have contractual principal amounts and for which the fair value option has been elected.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 18
-Subparagraph d(1)

+ Details

Name:	us-gaap_FairValueOptionAggregateDifferencesLoansAndLongTermReceivables
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 60
-Paragraph 47

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Subparagraph c
-Article 7

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateCommercialAndConsumerNet
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant