Investments (Changes in Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance at January 1,	$ 8,655	$ 13,662	$ 12,650
Changes In Net Unrealized Investment Gains Losses Related To Cumulative Effects Of Changes In Accounting Principles, Net Of Income Tax	21	1,258	0
Fixed maturity securities AFS on which noncredit OTTI losses have been recognized	8	(16)	33
Unrealized investment gains (losses) during the year	18,770	(10,367)	804
Unrealized investment gains (losses) relating to:
Future policy benefits	(1,050)	108	1,037
DAC and VOBA related to noncredit OTTI losses recognized in AOCI	0	0	3
DAC, VOBA and DSI	(1,485)	537	(338)
Policyholder dividend obligation	(1,592)	1,693	(190)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	(1)	9	(11)
Deferred income tax benefit (expense)	(3,339)	1,773	(324)
Net unrealized investment gains (losses)	19,987	8,657	13,664
Net unrealized investment gains (losses) attributable to noncontrolling interests	(6)	(2)	(2)
Balance at December 31,	19,981	8,655	13,662
Change in net unrealized investment gains (losses)	11,332	(5,005)	1,014
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	(6)	(2)	(2)
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 11,326	$ (5,007)	$ 1,012