Investments (Details Textuals 5)	Dec. 31, 2012	Dec. 31, 2011
Investments [Abstract]
Percentage of Mortgage Loans Classified as Performing	99.00%	99.00%

The percentage of all mortgage loans that are classified as performing.

No definition available.

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