Investments (Changes in Net Unrealized Investment Gains Losses) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance, beginning of period	$ 8,655
Cumulative effects of changes in accounting principles, net of income tax	21
Fixed maturity securities AFS on which noncredit OTTI losses have been recognized	4
Unrealized investment gains (losses) during the period	8,304
Unrealized investment gains (losses) relating to:
Future policy benefits	(253)
DAC, VOBA and DSI	(681)
Policyholder dividend obligation	(688)
Deferred income tax benefit (expense) related to noncredit OTTI losses recognized in AOCI	(1)
Deferred income tax benefit (expense)	(1,497)
Net unrealized investment gains (losses)	13,864
Net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Balance, end of period	13,862
Change in net unrealized investment gains (losses)	5,209
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 5,207