Investments (Changes in Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance at January 1,	$ 13,662	$ 12,650	$ 11,769
Changes In Net Unrealized Investment Gains Losses Related To Cumulative Effects Of Changes In Accounting Principles, Net Of Income Tax	1,258	0	0
Fixed maturity securities AFS on which noncredit OTTI losses have been recognized	(16)	33	84
Unrealized investment gains (losses) during the year	(10,367)	804	2,544
Unrealized investment gains (losses) relating to:
Future policy benefits	108	1,037	(951)
DAC and VOBA related to noncredit OTTI losses recognized in AOCI	0	3	(3)
DAC, VOBA and DSI	537	(338)	(157)
Policyholder dividend obligation	1,693	(190)	(148)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	9	(11)	(28)
Deferred income tax benefit (expense)	1,773	(324)	(485)
Net unrealized investment gains (losses)	8,657	13,664	12,625
Net unrealized investment gains (losses) attributable to noncontrolling interests	(2)	(2)	25
Balance at December 31,	8,655	13,662	12,650
Change in net unrealized investment gains (losses)	(5,005)	1,014	856
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	(2)	(2)	25
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ (5,007)	$ 1,012	881
Changes in Net unrealized gains (losses) attributable to MetLife related to investments, derivatives, DAC, VOBA, DSI, and future policy benefits			$ (304)