Investments (Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Components of net unrealized investment gains (losses) included in accumulated other comprehensive income
Fixed maturity securities AFS	$ 31,195	$ 44,415
Derivatives	2,031	1,924
Other	354	267
Subtotal	33,580	46,606
Policyholder liabilities	(5,245)	(10,797)
DAC, VOBA and DSI	(3,274)	(4,050)
Subtotal	(8,519)	(14,847)
Deferred income tax benefit (expense)	(6,380)	(8,009)
Net unrealized investment gains (losses)	18,681	23,750
Net unrealized investment gains (losses) attributable to noncontrolling interests	(23)	(20)
Net unrealized investment gains (losses) attributable to MetLife, Inc.	$ 18,658	$ 23,730