Insurance (Obligations Under Funding Agreements - Narrative) (Details) - USD ($) $ in Billions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Insurance [Abstract]
Funding agreements issued to certain SPEs	$ 41.1	$ 48.1	$ 48.9
Funding agreements repaid to certain SPEs	42.0	49.9	$ 45.6
Outstanding funding agreements to certain SPEs	$ 30.9	$ 31.6

Amount of funding agreements issued during current year 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_FundingAgreementsIssuedToCertainSpecialPurposeEntities
Namespace Prefix:	met_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration