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, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Weighted Average Shares:
Weighted average common stock outstanding - basic	946.2		1,015.6		951.3	1,025.7
Incremental common shares from assumed exercise or issuance of stock-based awards	6.7		8.2		6.8	8.3
Weighted average common stock outstanding - diluted	952.9		1,023.8		958.1	1,034.0
Net Income (Loss):
Net income (loss)	$ 1,746	$ 1,385	$ 894	$ 1,257	$ 3,131	$ 2,151
Less: Net income (loss) attributable to noncontrolling interests	5		3		9	7
Less: Preferred stock dividends	57	$ 32	46	$ 6	89	52
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 1,684		$ 845		$ 3,033	$ 2,092
Basic	$ 1.78		$ 0.83		$ 3.19	$ 2.04
Diluted	$ 1.77		$ 0.83		$ 3.17	$ 2.02