Investments (Changes in Net Unrealized Investment Gains Losses) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance, beginning of period	$ 17,671
Unrealized investment gains (losses) during the period	(23,300)
Unrealized investment gains (losses) relating to:
Policyholder liabilities	4,551
DAC, VOBA and DSI	2,465
Deferred income tax benefit (expense)	3,794
Net unrealized investment gains (losses)	5,181
Net unrealized investment gains (losses) attributable to noncontrolling interests	1
Balance, end of period	5,182
Change in net unrealized investment gains (losses)	(12,490)
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	1
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ (12,489)