Investments (Details 13) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Components of net unrealized investment gains (losses) included in accumulated other comprehensive loss
Fixed maturity securities that were temporarily impaired	$ 33,589	$ 21,096
Fixed maturity securities with noncredit OTTI losses in accumulated other comprehensive income (loss)	(441)	(724)	(601)
Total fixed maturity securities	33,148	20,372
Equity securities	15	(167)
Derivatives	1,508	1,514
Other	(11)	72
Subtotal	34,660	21,791
Insurance liability loss recognition	(6,902)	(3,996)
DAC and VOBA related to noncredit OTTI losses recognized in accumulated other comprehensive income (loss)	25	47
DAC and VOBA	(2,616)	(1,800)
Policyholder dividend obligation	(3,909)	(2,919)
Subtotal	(13,402)	(8,668)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in accumulated other comprehensive income (loss)	145	236
Deferred income tax benefit (expense)	(7,652)	(4,694)
Net unrealized investment gains (losses)	13,751	8,665
Net unrealized investment gains (losses) attributable to noncontrolling interests	1	9
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 13,752	$ 8,674