Earnings Per Common Share (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Shares:
Weighted average common stock outstanding - basic	862.7	907.8	937.6
Incremental common shares from assumed exercise or issuance of stock-based awards	6.7	5.4	6.8
Weighted average common stock outstanding - diluted	869.4	913.2	944.4
Net Income (Loss):
Net income (loss)	$ 6,575	$ 5,418	$ 5,909
Less: Net income (loss) attributable to noncontrolling interests	21	11	10
Less: Preferred stock dividends	195	202	178
Preferred stock redemption premium	6	14	0
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 6,353	$ 5,191	$ 5,721
Basic	$ 7.36	$ 5.72	$ 6.10
Diluted	$ 7.31	$ 5.68	$ 6.06