Junior Subordinated Debt Securities (Junior Subordinated Debt Securities) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Face Value		$ 3,200
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (90)	(88)
Junior Subordinated Notes	3,153	3,150
MetLife Inc $500M Maturing 2069 [Member]
Debt Instrument [Line Items]
Face Value	500	500
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (6)	(7)
Debt Instrument, Interest Rate, Stated Percentage	10.75%
Debt Instrument, Interest Rate Terms	LIBOR + 7.548%
Junior Subordinated Notes	$ 494	493
Senior notes
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (85)	(81)
Debt Instrument, Interest Rate, Stated Percentage	5.70%
MetLife Capital Trust X $750M Maturing 2068 [Member]
Debt Instrument [Line Items]
Face Value	$ 750	750
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (10)	(10)
Debt Instrument, Interest Rate, Stated Percentage	9.25%
Debt Instrument, Interest Rate Terms	LIBOR + 5.540%
Junior Subordinated Notes	$ 740	740
MetLife Capital Trust IV $700M Maturing 2067 [Member]
Debt Instrument [Line Items]
Face Value	700	700
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (14)	(15)
Debt Instrument, Interest Rate, Stated Percentage	7.875%
Debt Instrument, Interest Rate Terms	LIBOR + 3.960%
Junior Subordinated Notes	$ 686	685
MetLife Inc $1,250M Maturing 2066 [Member]
Debt Instrument [Line Items]
Face Value	1,250	1,250
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (17)	(18)
Debt Instrument, Interest Rate, Stated Percentage	6.40%
Debt Instrument, Interest Rate Terms	LIBOR + 2.205%
Junior Subordinated Notes	$ 1,233	1,232
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Face Value	3,200
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (47)	$ (50)

Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Junior Subordinated Notes, which have a lower priority than senior instruments.

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