Investments (Changes in Net Unrealized Investment Gains Losses) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($)
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance, beginning of period	$ 23,730
Unrealized investment gains (losses) during the period	(11,207)
Unrealized investment gains (losses) relating to:
Policyholder liabilities	3,935
DAC, VOBA and DSI	599
Deferred income tax benefit (expense)	1,553
Net unrealized investment gains (losses)	18,610
Net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Balance, end of period	18,608
Change in net unrealized investment gains (losses)	(5,120)
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	(2)
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ (5,122)