Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 19,028	$ 15,866	$ 16,623	$ 15,388	$ 15,608	$ 22,283	$ 15,474	$ 15,405	$ 66,905	$ 68,770	$ 68,696
Total expenses	18,087	15,332	16,193	15,131	13,582	20,868	14,486	13,470	64,743	62,406	60,178
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
Net income (loss) attributable to MetLife, Inc.	607	489	402	80	1,578	1,162	910	1,634	1,578	5,284	6,855
Less: Preferred stock dividends	33	67	32	66	29	64	29	63	198	185	195
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 earnings per common share
Net income (loss) attributable to MetLife, Inc. (in dollars per share)	$ 0.82	$ 0.65	$ 0.52	$ 0.10	$ 2.01	$ 1.46	$ 1.12	$ 1.98
Net income (loss) available to MetLife, Inc.’s common shareholders (in dollars per share)	0.78	0.56	0.48	0.02	1.98	1.38	1.09	1.91	$ 1.82	$ 6.35	$ 7.71
Diluted earnings per common share
Net income (loss) attributable to MetLife, Inc. (in dollars per share)	0.82	0.65	0.52	0.10	2.00	1.45	1.12	1.97
Net income (loss) available to MetLife, Inc.’s common shareholders (in dollars per share)	$ 0.77	$ 0.56	$ 0.48	$ 0.02	$ 1.96	$ 1.37	$ 1.08	$ 1.89	$ 1.81	$ 6.30	$ 7.65