Condensed Financial Information (Parent Company) (Condensed Statements of Operations) (Details) - USD ($) $ 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
Condensed Income Statements, Captions [Line Items]
Net investment income									$ 19,908	$ 15,916	$ 21,395
Other revenues									2,526	2,630	2,619
Net investment gains (losses)									(2,824)	(1,260)	1,543
Net derivative gains (losses)									(2,140)	(2,251)	(3,257)
Total revenues	$ 19,028	$ 15,866	$ 16,623	$ 15,388	$ 15,608	$ 22,283	$ 15,474	$ 15,405	66,905	68,770	68,696
Expenses
Other expenses									12,710	11,859	12,018
Total expenses	18,087	15,332	16,193	15,131	13,582	20,868	14,486	13,470	64,743	62,406	60,178
Income (loss) before provision for income tax and equity in earnings of subsidiaries									2,162	6,364	8,518
Provision for income tax expense (benefit)									560	1,062	1,642
Equity in earnings of subsidiaries									151	1,305	5,136
Net income (loss)	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
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
Comprehensive income (loss)									4,957	(14,886)	4,089
Parent Company
Condensed Income Statements, Captions [Line Items]
Net investment income									188	58	25
Other revenues									17	17	19
Net investment gains (losses)									134	332	1,655
Net derivative gains (losses)									(41)	129	116
Total revenues									298	536	1,815
Expenses
Interest expense									907	829	847
Other expenses									140	79	207
Total expenses									1,047	908	1,054
Income (loss) before provision for income tax and equity in earnings of subsidiaries									(749)	(372)	761
Provision for income tax expense (benefit)									(128)	(37)	202
Equity in earnings of subsidiaries									2,199	5,619	6,296
Net income (loss)									1,578	5,284	6,855
Less: Preferred stock dividends									198	185	195
Preferred stock redemption premium									0	0	6
Net income (loss) available to MetLife, Inc.’s common shareholders									1,380	5,099	6,654
Comprehensive income (loss)									$ 4,957	$ (14,886)	$ 4,089