Equity (Stock-Based Compensation Plans - Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
2005 Stock and Incentive Compensation Plan [Member]
Equity - Stock-based Compensation Plans [Line Items]
Aggregate number of shares authorized for issuance	68,000,000
Shares available for grant	20,098,440
Stock Options [Member]
Equity - Stock-based Compensation Plans [Line Items]
Vesting period	3 years
Award Expiration Date	10 years
Closing share price	$ 53.92	$ 32.94
Stock Options [Member] \| Phantom Share Units [Member]
Equity - Stock-based Compensation Plans [Line Items]
Awards granted	48,301
Stock Options [Member] \| Phantom Share Units [Member] \| Minimum [Member]
Equity - Stock-based Compensation Plans [Line Items]
Vesting period	1 year
Stock Options [Member] \| Phantom Share Units [Member] \| Maximum [Member]
Equity - Stock-based Compensation Plans [Line Items]
Vesting period	3 years
2005 Non-Management Director Stock Compensation Plan [Member]
Equity - Stock-based Compensation Plans [Line Items]
Aggregate number of shares authorized for issuance	2,000,000
Shares available for grant	1,695,352
Performance Shares [Member]
Equity - Stock-based Compensation Plans [Line Items]
Vesting period	3 years
Awards granted	1,749,212
Performance Shares to which performance factor will be applied	1,545,020
Performance Factor		0.92
Performance Shares [Member] \| Minimum [Member]
Equity - Stock-based Compensation Plans [Line Items]
Performance Factor		0.0
Future Performance Factor	0.00
Performance Shares [Member] \| Maximum [Member]
Equity - Stock-based Compensation Plans [Line Items]
Performance Factor		2.0
Future Performance Factor	1.75
Performance Shares [Member] \| Phantom Share Units [Member]
Equity - Stock-based Compensation Plans [Line Items]
Awards granted	297,834
Restricted Stock Units [Member]
Equity - Stock-based Compensation Plans [Line Items]
Vesting period	3 years
Awards granted	2,182,213
Restricted Stock Units [Member] \| Phantom Share Units [Member]
Equity - Stock-based Compensation Plans [Line Items]
Vesting period	3 years
Awards granted	445,740
Other Restricted Stock Units [Member]
Equity - Stock-based Compensation Plans [Line Items]
Vesting period	5 years

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

No definition available.

Name:	met_FuturePerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	met_PerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The date when the equity-based award expires as specified in the award agreement, presented in number of years.

+ References

No definition available.

+ Details

Name:	met_ShareBasedCompensationArrangementByShareBasedPaymentAwardExpirationDateYears
Namespace Prefix:	met_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share based payment award equity instruments other than option vested in period.

+ References

No definition available.

+ Details

Name:	met_ShareBasedPaymentAwardEquityInstrumentsOtherThanOptionVestedInPeriod
Namespace Prefix:	met_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Period 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, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant