Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of net unrealized investment gains (losses) included in accumulated other comprehensive loss
Fixed maturity securities AFS	$ 11,356	$ 22,645	$ 20,330
Fixed maturity securities AFS with noncredit OTTI losses included in AOCI	25	41	8
Total fixed maturity securities AFS	11,381	22,686	20,338
Equity securities	0	421	485
Derivatives	2,127	1,453	2,923
Other	290	46	23
Subtotal	13,798	24,606	23,769
Future policy benefits	31	(77)	(1,114)
DAC and VOBA related to noncredit OTTI losses recognized in AOCI	0	0	(3)
DAC, VOBA and DSI	(1,231)	(1,768)	(1,430)
Policyholder dividend obligation	(428)	(2,121)	(1,931)
Subtotal	(1,628)	(3,966)	(4,478)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	(3)	(12)	(1)
Deferred income tax benefit (expense)	(3,502)	(6,958)	(6,634)
Net unrealized investment gains (losses)	8,665	13,670	12,656
Net unrealized investment gains (losses) attributable to noncontrolling interests	(10)	(8)	(6)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 8,655	$ 13,662	12,650	$ 11,769
Net unrealized gains (losses) attributable to MetLife related to investments, derivatives , DAC, VOBA, DSI, and future policy benefits			$ 1,250