Earnings Per Common Share (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Weighted Average Shares:
Weighted average common stock outstanding - basic	809.7		873.3		816.7	879.3
Incremental common shares from assumed exercise or issuance of stock-based awards	4.8		6.4		5.8	6.5
Weighted average common stock outstanding - diluted	814.5		879.7		822.5	885.8
Net Income (Loss):
Net income (loss)	$ 138	$ 674	$ 3,412	$ 363	$ 812	$ 3,775
Less: Net income (loss) attributable to noncontrolling interests	6		5		11	10
Less: Preferred stock dividends	29	$ 63	35	$ 68	92	103
Preferred stock redemption premium	0		6		0	6
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 103		$ 3,366		$ 709	$ 3,656
Basic	$ 0.13		$ 3.85		$ 0.87	$ 4.16
Diluted	$ 0.13		$ 3.83		$ 0.86	$ 4.13