Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Components of net unrealized investment gains (losses) included in accumulated other comprehensive loss
Fixed maturity securities	$ 17,545	$ 22,645
Fixed maturity securities with noncredit OTTI losses included in AOCI	35	41
Total fixed maturity securities	17,580	22,686
Equity securities	0	421
Derivatives	936	1,453
Other	136	46
Subtotal	18,652	24,606
Future policy benefits	(138)	(77)
DAC, VOBA and DSI	(1,304)	(1,768)
Policyholder dividend obligation	(1,277)	(2,121)
Subtotal	(2,719)	(3,966)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	(5)	(12)
Deferred income tax benefit (expense)	(4,372)	(6,958)
Net unrealized investment gains (losses)	11,556	13,670
Net unrealized investment gains (losses) attributable to noncontrolling interests	(9)	(8)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 11,547	$ 13,662