Investments (Details Textuals 32) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Investments [Abstract]
Noncredit loss component of OTTI losses for foreign corporate securities was in an unrealized gain (loss) position	$ 1

Noncredit portion of OTTI losses that is included in accumulated OCI. Noncredit loss component of OTTI losses for foreign corporate securities was in an unrealized gain (loss) position.

No definition available.

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