Investments (Changes in Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Balance at January 1,	$ 23,730	$ 19,981	$ 8,655
Cumulative effects of changes in accounting principles, net of income tax	0	0	21
Unrealized investment gains (losses) during the year	(14,695)	14,004	18,778
Unrealized investment gains (losses) relating to:
Policyholder liabilities	5,819	(7,758)	(2,642)
DAC, VOBA and DSI	842	(1,334)	(1,485)
Deferred income tax benefit (expense)	1,978	(1,159)	(3,340)
Net unrealized investment gains (losses)	17,674	23,734	19,987
Net unrealized investment gains (losses) attributable to noncontrolling interests	(3)	(4)	(6)
Balance at December 31,	17,671	23,730	19,981
Change in net unrealized investment gains (losses)	(6,056)	3,753	11,332
Change in net unrealized investment gains (losses) attributable to noncontrolling interests	(3)	(4)	(6)
Change in net unrealized investment gains (losses) attributable to MetLife, Inc.	$ (6,059)	$ 3,749	$ 11,326