Earnings Per Common Share (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Weighted Average Shares:
Weighted average common stock outstanding - basic									757.7	803.2	862.7
Incremental common shares from assumed exercise or issuance of stock-based awards									4.6	5.7	6.7
Weighted average common stock outstanding - diluted									762.3	808.9	869.4
Net Income (Loss):
Net income (loss)	$ 614	$ 495	$ 408	$ 85	$ 1,581	$ 1,167	$ 915	$ 1,639	$ 1,602	$ 5,302	$ 6,876
Less: Net income (loss) attributable to noncontrolling interests	7	6	6	5	3	5	5	5	24	18	21
Less: Preferred stock dividends	33	67	32	66	29	64	29	63	198	185	195
Preferred stock redemption premium									0	0	6
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 574	$ 422	$ 370	$ 14	$ 1,549	$ 1,098	$ 881	$ 1,571	$ 1,380	$ 5,099	$ 6,654
Basic	$ 0.78	$ 0.56	$ 0.48	$ 0.02	$ 1.98	$ 1.38	$ 1.09	$ 1.91	$ 1.82	$ 6.35	$ 7.71
Diluted	$ 0.77	$ 0.56	$ 0.48	$ 0.02	$ 1.96	$ 1.37	$ 1.08	$ 1.89	$ 1.81	$ 6.30	$ 7.65