Equity (Details Textuals 2) (Performance Shares [Member])	6 Months Ended	12 Months Ended
Jun. 30, 2011	Dec. 31, 2010
Performance Shares [Member]
Equity - Stock-Based Compensation (Textuals) [Abstract]
Vesting period		3 years
Performance Shares, performance factor lower range		0.0
Performance Shares, performance factor upper range		2.0
Performance Shares Factor Percentage		90.00%
Outstanding Performance Shares to which the final performance factor will be applied		824,825
Common stock shares issued for performance share awards	742,343

Outstanding Performance Shares to which the final performance factor will be applied.

Name:	met_OutstandingPerformanceSharesToWhichFinalPerformanceFactorWillBeApplied
Namespace Prefix:	met
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of the performance factor for the three year performance period.

+ Details

Name:	met_PerformanceSharesFactorPercentage
Namespace Prefix:	met
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The lower range performance factor range used to determine final number of performance shares payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

+ Details

Name:	met_PerformanceSharesPerformanceFactorLowerRangeLimit
Namespace Prefix:	met
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The upper range performance factor range used to determine final number of performance shares payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

+ Details

Name:	met_PerformanceSharesPerformanceFactorUpperRangeLimit
Namespace Prefix:	met
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ShareBasedCompensationAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph a

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod
Namespace Prefix:	us-gaap
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares issued during the period as a result of any share-based compensation plan other than an employee stock ownership plan (ESOP).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 10

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 5

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation
Namespace Prefix:	us-gaap
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration