Insurance (Details Textuals 3) (USD $) In Billions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Insurance [Abstract]
Issued funding agreements to certain SPEs	$ 39.9	$ 34.1	$ 28.6
Repaid funding agreements to certain SPEs	41.6	30.9	32.0
Outstanding funding agreements to certain SPEs	$ 25.5	$ 27.2

Amount of funding agreements during current year issued to certain special purpose entities that have issued debt securities for which payment of interest and principal is secured by such funding agreements.

No definition available.

Name:	met_IssuedFundingAgreementsToCertainSpecialPurposeEntities
Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration