Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Components of net unrealized investment gains (losses) included in accumulated other comprehensive income
Fixed maturity securities AFS	$ 28,447	$ 44,415
Derivatives	656	1,924
Other	194	267
Subtotal	29,297	46,606
Policyholder liabilities	(3,989)	(10,797)
DAC, VOBA and DSI	(2,781)	(4,050)
Subtotal	(6,770)	(14,847)
Deferred income tax benefit (expense)	(5,794)	(8,009)
Net unrealized investment gains (losses)	16,733	23,750
Net unrealized investment gains (losses) attributable to noncontrolling interests	(21)	(20)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 16,712	$ 23,730