Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Components of net unrealized investment gains (losses) included in accumulated other comprehensive income
Fixed maturity securities AFS	$ 33,813	$ 44,415
Derivatives	1,353	1,924
Other	233	267
Subtotal	35,399	46,606
Policyholder liabilities	(6,862)	(10,797)
DAC, VOBA and DSI	(3,451)	(4,050)
Subtotal	(10,313)	(14,847)
Deferred income tax benefit (expense)	(6,456)	(8,009)
Net unrealized investment gains (losses)	18,630	23,750
Net unrealized investment gains (losses) attributable to noncontrolling interests	(22)	(20)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 18,608	$ 23,730