Condensed Financial Information (Parent Company) (Condensed Statements of Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Income Statements, Captions [Line Items]
Net investment income	$ 21,395	$ 17,117	$ 18,868
Other revenues	2,619	1,849	1,842
Net investment gains (losses)	1,529	(110)	444
Net derivative gains (losses)	(2,228)	1,349	628
Total revenues	71,080	67,842	69,620
Expenses
Other expenses	12,586	13,150	13,689
Total expenses	62,954	60,915	62,825
Income (loss) before provision for income tax and equity in earnings of subsidiaries	8,126	6,927	6,795
Provision for income tax expense (benefit)	1,551	1,509	886
Equity in earnings of subsidiaries	5,100	829	795
Net income (loss)	6,554	5,407	5,899
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
Comprehensive income (loss)	(599)	10,427	17,208
Parent Company
Condensed Income Statements, Captions [Line Items]
Net investment income	25	50	77
Other revenues	19	29	27
Net investment gains (losses)	1,655	(154)	(40)
Net derivative gains (losses)	116	(61)	(45)
Total revenues	1,815	(136)	19
Expenses
Interest expense	847	833	850
Other expenses	207	154	153
Total expenses	1,054	987	1,003
Income (loss) before provision for income tax and equity in earnings of subsidiaries	761	(1,123)	(984)
Provision for income tax expense (benefit)	202	(267)	(582)
Equity in earnings of subsidiaries	5,995	6,263	6,301
Net income (loss)	6,554	5,407	5,899
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
Comprehensive income (loss)	$ (599)	$ 10,427	$ 17,208