Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of net unrealized investment gains (losses) included in accumulated other comprehensive income
Fixed maturity securities AFS	$ 29,461	$ 44,415	$ 30,083
Derivatives	2,061	1,924	2,209
Other	389	267	310
Subtotal	31,911	46,606	32,602
Policyholder liabilities	(4,978)	(10,797)	(3,039)
DAC, VOBA and DSI	(3,208)	(4,050)	(2,716)
Subtotal	(8,186)	(14,847)	(5,755)
Deferred income tax benefit (expense)	(6,031)	(8,009)	(6,850)
Net unrealized investment gains (losses)	17,694	23,750	19,997
Net unrealized investment gains (losses) attributable to noncontrolling interests	(23)	(20)	(16)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 17,671	$ 23,730	$ 19,981	$ 8,655