Earnings Per Common Share (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Weighted Average Shares:
Weighted average common stock outstanding - basic	751.4	795.8			764.1	809.7
Incremental common shares from assumed exercise or issuance of stock-based awards	4.1	4.9			4.6	5.5
Weighted average common stock outstanding - diluted	755.5	800.7			768.7	815.2
Net Income (Loss):
Net income (loss)	$ 495	$ 1,167	$ 493	$ 2,554	$ 988	$ 3,721
Less: Net income (loss) attributable to noncontrolling interests	6	5			17	15
Less: Preferred stock dividends	67	64	$ 98	$ 92	165	156
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 422	$ 1,098			$ 806	$ 3,550
Basic	$ 0.56	$ 1.38			$ 1.05	$ 4.38
Diluted	$ 0.56	$ 1.37			$ 1.05	$ 4.35