Earnings Per Common Share (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Weighted Average Shares:
Weighted average common stock outstanding - basic	914.1	956.5
Incremental common shares from assumed exercise or issuance of stock-based awards	5.9	6.8
Weighted average common stock outstanding - diluted	920.0	963.3
Net Income (Loss):
Net income (loss)	$ 4,401	$ 1,385
Less: Net income (loss) attributable to noncontrolling interests	3	4
Less: Preferred stock dividends	32	32
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 4,366	$ 1,349
Basic	$ 4.78	$ 1.41
Diluted	$ 4.75	$ 1.40