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, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Weighted Average Shares:
Weighted average common stock outstanding - basic	765.9		809.7		770.6	816.7
Incremental common shares from assumed exercise or issuance of stock-based awards	3.7		4.8		4.8	5.8
Weighted average common stock outstanding - diluted	769.6		814.5		775.4	822.5
Net Income (Loss):
Net income (loss)	$ 408	$ 85	$ 915	$ 1,639	$ 493	$ 2,554
Less: Net income (loss) attributable to noncontrolling interests	6		5		11	10
Less: Preferred stock dividends	32	$ 66	29	$ 63	98	92
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 370		$ 881		$ 384	$ 2,452
Basic	$ 0.48		$ 1.09		$ 0.50	$ 3.00
Diluted	$ 0.48		$ 1.08		$ 0.50	$ 2.98