Consolidated Statements of Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock at Cost	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment [Member]	Total MetLife, Inc.'s Stockholders' Equity	Total MetLife, Inc.'s Stockholders' Equity Cumulative Effect, Period of Adoption, Adjustment [Member]	Noncontrolling Interests
Beginning Balance at Dec. 31, 2017	$ 58,870	$ 7	$ 0	$ 12	$ 31,111	$ 26,527	$ (905)	$ (6,401)	$ 7,427	$ 912	$ 58,676	$ 7	$ 194
Preferred stock redemption premium	0
Preferred stock issuance	1,274				1,274						1,274
Treasury stock acquired in connection with share repurchases	(3,992)							(3,992)			(3,992)
Stock-based compensation	89				89						89
Dividends on preferred stock	$ (141)					(141)					(141)
Dividend Per Share	$ 1.660
Dividends on common stock	$ (1,678)					(1,678)					(1,678)
Change in equity of noncontrolling interests	16										0		16
Net income (loss)	5,128					5,123					5,123		5
Other comprehensive income (loss), net of income tax	(6,615)								(6,617)		(6,617)		2
Ending Balance at Dec. 31, 2018	52,958	95	0	12	32,474	28,926	74	(10,393)	1,722	$ 21	52,741	95	217
Preferred stock redemption premium	0
Preferred stock issuance	0
Treasury stock acquired in connection with share repurchases	(2,285)							(2,285)			(2,285)
Stock-based compensation	206				206						206
Dividends on preferred stock	$ (178)					(178)					(178)
Dividend Per Share	$ 1.740
Dividends on common stock	$ (1,643)					(1,643)					(1,643)
Change in equity of noncontrolling interests	5										0		5
Net income (loss)	5,909					5,899					5,899		10
Other comprehensive income (loss), net of income tax	11,315								11,309		11,309		6
Ending Balance at Dec. 31, 2019	66,382	$ (121)	0	12	32,680	33,078	$ (121)	(12,678)	13,052		66,144	$ (121)	238
Redemption of preferred stock	(989)				(989)						(989)
Preferred stock redemption premium	(14)					(14)					(14)
Preferred stock issuance	1,961				1,961						1,961
Treasury stock acquired in connection with share repurchases	(1,151)							(1,151)			(1,151)
Stock-based compensation	160				160						160
Dividends on preferred stock	$ (202)					(202)					(202)
Dividend Per Share	$ 1.820
Dividends on common stock	$ (1,657)					(1,657)					(1,657)
Change in equity of noncontrolling interests	5										0		5
Net income (loss)	5,418					5,407					5,407		11
Other comprehensive income (loss), net of income tax	5,025								5,020		5,020		5
Ending Balance at Dec. 31, 2020	$ 74,817		$ 0	$ 12	$ 33,812	$ 36,491		$ (13,829)	$ 18,072		$ 74,558		$ 259