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, 2019	Sep. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Weighted Average Shares:
Weighted average common stock outstanding - basic	929.6	992.7			944.0	1,014.6
Incremental common shares from assumed exercise or issuance of stock-based awards	6.8	8.0			6.8	8.2
Weighted average common stock outstanding - diluted	936.4	1,000.7			950.8	1,022.8
Net Income (Loss):
Net income (loss)	$ 2,190	$ 915	$ 3,131	$ 2,151	$ 5,321	$ 3,066
Less: Net income (loss) attributable to noncontrolling interests	6	3			15	10
Less: Preferred stock dividends	32	32	$ 89	$ 52	121	84
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 2,152	$ 880			$ 5,185	$ 2,972
Basic	$ 2.31	$ 0.89			$ 5.49	$ 2.93
Diluted	$ 2.30	$ 0.88			$ 5.45	$ 2.91