Equity (Details 10) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other comprehensive income (loss):
Other comprehensive income (loss)	$ 4,848	$ 4,011	$ 11,260
Holding gains (losses) on investments arising during the year	13,945	10,092	18,548
Income tax effect of holding gains (losses)	(4,783)	(3,516)	(6,243)
Reclassification adjustments
Reclassification adjustments for recognized holding (gains) losses included in current year income	755	(733)	1,464
Income tax effect	(260)	255	(493)
Unrealized investment loss of subsidiary at date of sale	(105)	0	0
Income tax on unrealized investment loss of subsidiary at date of sale	37	0	0
Allocation of holding (gains) losses on investments relating to other policyholder amounts	(6,339)	(2,813)	(2,979)
Income tax effect of allocation of holding (gains) losses to other policyholder amounts	2,174	980	1,002
Allocation of holding (gains) losses on investments relating to other policyholder amounts of subsidiary at date of sale	93	0	0
Income tax effect of allocation of holding (gains) losses to other policyholder amounts of subsidiary at date of sale	(33)	0	0
Net unrealized investment gains (losses), net of income	5,484	4,265	11,299
Foreign currency translation adjustments, net of income tax	(135)	(350)	63
Foreign currency translation adjustments of subsidiary at date of sale	(7)	0	0
Defined benefit plans adjustment, net of income tax	(494)	96	(102)
Other comprehensive income (loss) attributable to noncontrolling interests	38	(5)	11
Cumulative effect of change in accounting principles, net of income tax	0	52	(76)
Other comprehensive income (loss) attributable to MetLife, Inc.	4,886	4,058	11,195
Other Comprehensive Income (Loss), Effect of Change in Accounting Principle, Taxes	0	27	40
Total MetLife, Inc.'s Stockholders' Equity
Other comprehensive income (loss):
Other comprehensive income (loss)	4,886	4,006	11,271
Reclassification adjustments
Defined benefit plans adjustment, net of income tax	$ (494)	$ 96	$ (102)