Total realized and unrealized gains and losses credited to the annuity and insurance contracts.

No definition available.

Name:	met_DefinedBenefitPlanInvestmentIncomeLossFromAnnuityAndLifeInsuranceContracts
Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Total revenue from defined benefit plan assets held in annuity and life insurance contracts recognized in consolidated statement of operations and includes policy charges, net investment income from investments backing the contracts and administrative fees.

+ References

No definition available.

+ Details

Name:	met_DefinedBenefitPlanRevenueFromAnnuityAndLifeInsuranceContracts
Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This item represents the percentage of the Subsidiaries' obligations that result from benefits calculated with the traditional formula.

+ References

No definition available.

+ Details

Name:	met_PercentageOfBenefitsCalculatedWithTraditionalFormula
Namespace Prefix:	met_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512013

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Projected Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6522206

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Postretirement Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6503904

+ Details

Name:	us-gaap_DefinedBenefitPlanBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanFutureAmortizationOfGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount included in accumulated other comprehensive income (AOCI) related to prior service cost (credit) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanFutureAmortizationOfPriorServiceCostCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=met_UnitedStatesPensionPlanofUSEntityNonQualifiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=met_UnitedStatesPensionPlanofUSEntityQualifiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_ForeignPensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_ForeignPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_UnitedStatesPostretirementBenefitPlansOfUSEntityDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Percentage of benefits calculated with the traditional formula	89.00%
Total revenue from annuity and life insurance contracts recognized	$ 50	$ 49	$ 54
Total investment income (loss) from annuity and life insurance contracts	1,200	20	867
Defined Contribution Plan, Cost Recognized	77	93	96
Pension Benefits U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate projected benefit obligations	10,262	8,591	9,480
Estimated net actuarial losses amortized into net periodic benefit cost over the next year	200
Estimated prior service cost amortized into net periodic benefit cost over the next year	(1)
Weighted average expected return on plan assets	6.25%	6.25%	7.00%
Pension Benefits U.S. Plans [Member] \| Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected return on plan assets				6.24%
Pension Benefits Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate projected benefit obligations	739	744	823
Weighted average expected return on plan assets	3.24%	2.07%	3.35%
Pension Benefits Non-U.S. Plans [Member] \| Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected return on plan assets				2.73%
Other Postretirement Benefits U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate projected benefit obligations	2,110	1,834	2,375
Estimated net actuarial losses amortized into net periodic benefit cost over the next year	31
Estimated prior service cost amortized into net periodic benefit cost over the next year	(4)
Weighted average expected return on plan assets	5.70%	5.76%	6.26%
Expected future discretionary contributions	50
Other Postretirement Benefits U.S. Plans [Member] \| Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected return on plan assets				5.65%
Other Postretirement Benefits Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate projected benefit obligations	35	41	43
Weighted average expected return on plan assets	7.25%	7.25%	6.54%
Other Postretirement Benefits Non-U.S. Plans [Member] \| Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted average expected return on plan assets				6.75%
United States Pension Plan of US Entity, Qualified [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future discretionary contributions	300
United States Pension Plan of US Entity, Non Qualified [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate projected benefit obligations	1,300	1,000
Expected future discretionary contributions	$ 70