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, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Weighted Average Shares:
Weighted average common stock outstanding - basic	908.8		946.2		911.5	951.3
Incremental common shares from assumed exercise or issuance of stock-based awards	4.3		6.7		5.0	6.8
Weighted average common stock outstanding - diluted	913.1		952.9		916.5	958.1
Net Income (Loss):
Net income (loss)	$ 150	$ 4,401	$ 1,746	$ 1,385	$ 4,551	$ 3,131
Less: Net income (loss) attributable to noncontrolling interests	5		5		8	9
Less: Preferred stock dividends	77	$ 32	57	$ 32	109	89
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 68		$ 1,684		$ 4,434	$ 3,033
Basic	$ 0.07		$ 1.78		$ 4.86	$ 3.19
Diluted	$ 0.07		$ 1.77		$ 4.84	$ 3.17