Investments (Details Textuals 32) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Investments [Abstract]
Equity securities other than temporary impairment losses recognized in earnings	$ 15	$ 6

This item represents the total equity security other than temporary impairment losses recognized in earnings, net.

No definition available.

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