Credit Facility.

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

- Definition

The dollar amount of long-term debt advances made from the Federal Home Loan Bank during the period.

+ Details

Name:	met_FederalHomeLoanBankAdvancesLongTermDebt
Namespace Prefix:	met
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The net dollar amount of debt advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ Details

Name:	met_FederalHomeLoanBankNetAdvancesTotalDebt
Namespace Prefix:	met
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The dollar amount of long-term debt repayments made to the Federal Home Loan Bank during the period.

+ Details

Name:	met_FederalHomeLoanBankRepaymentsLongTermDebt
Namespace Prefix:	met
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Letter Of Credit Facility Outstanding.

+ Details

Name:	met_LetterOfCreditFacilityOutstanding
Namespace Prefix:	met
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Cancellation of contract at a specified date.

+ Details

Name:	met_LineOfCreditFacilityCancellationDate
Namespace Prefix:	met
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

The term of a Credit Facility which may be presented in a variety of ways (years, months, days).

+ Details

Name:	met_LineOfCreditFacilityTerm
Namespace Prefix:	met
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-DEP
-Chapter 12
-Paragraph 26
-IssueDate 2006-05-01

+ Details

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

- Definition

Reflects when the credit facility first became available, which may be presented in a variety of ways (year, month and year, day, month and year, quarter).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityInitiationDate
Namespace Prefix:	us-gaap
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of the FHLB debt obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 15
-Subparagraph a

+ Details

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

- Definition

Carrying value as of the balance sheet date , including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 20, 22
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 9

+ Details

Name:	us-gaap_SecuredDebt
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Long-term and Short-term Debt (Details) (USD $)	6 Months Ended
Long-term and Short-term Debt (Details) (USD $)	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Credit Facility [Abstract]
Federal Home Loan Bank Stock	$ 221,000,000		$ 187,000,000
Federal Home Loan Bank, Liability for Debt Advances	4,500,000,000		3,800,000,000
Federal Home Loan Bank Advances Long Term Debt	1,205,000,000	678,000,000
Federal Home Loan Bank Repayments, Long Term Debt	340,000,000	169,000,000
Federal Home Loan Bank, Fair Value of collateral pledged for debt advances	7,100,000,000		7,800,000,000
Collateral financing arrangements	5,297,000,000		5,297,000,000
Missouri Reinsurance (Barbados) Inc. [Member] \| Committed Credit Facility Total [Member]
Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	350,000,000
Letter of Credit Outstanding	305,000,000
Line of Credit Facility, Initiation Date	February 2011
Credit Facility Term	1 year
Line of Credit Facility, Cancellation Date	July 1, 2011
Federal Home Loan Bank of New York [Member]
Credit Facility [Abstract]
Federal Home Loan Bank, Fair Value of collateral pledged for debt advances	20,589,000,000		21,975,000,000
General Credit Facility Total [Member]
Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	4,000,000,000
Letter of Credit Outstanding	1,500,000,000
Collateral financing arrangements	0
Unused Commitments	2,500,000,000
Committed Credit Facility Total [Member]
Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	12,800,000,000
Letter of Credit Outstanding	6,100,000,000
Collateral financing arrangements	2,800,000,000
Unused Commitments	$ 3,900,000,000