Derivatives (Net Derivative Gains Losses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components of Net Derivatives Gains (Losses)
Derivatives and hedging gains (losses)	$ 1,638met_DerivativesAndHedgingGainslosses	$ (8,343)met_DerivativesAndHedgingGainslosses	$ (3,158)met_DerivativesAndHedgingGainslosses
Embedded derivatives	(321)	5,104	1,239
Total net derivative gains (losses)	$ 1,317	$ (3,239)	$ (1,919)

This caption represents the net unrealized and realized gains (losses) on derivatives and hedged items recognized during the reporting period.

No definition available.

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- Definition

Net Increase or Decrease in the fair value of the embedded derivative or group of embedded derivatives included in earnings in the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

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- Definition

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959

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