Investments (Changes in Net Unrealized Investment Gains Losses) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance, beginning of period	$ 19,981
Fixed maturity securities AFS on which noncredit OTTI losses have been recognized	(33)
Unrealized investment gains (losses) during the period	10,517
Unrealized investment gains (losses) relating to:
Future policy benefits	(1,199)
DAC, VOBA and DSI	(954)
Policyholder dividend obligation	(778)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	4
Deferred income tax benefit (expense)	(1,623)
Net unrealized investment gains (losses)	25,915
Net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Balance, end of period	25,913
Change in net unrealized investment gains (losses)	5,934
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 5,932