Junior Subordinated Debt Securities (Junior Subordinated Debt Securities) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Feb. 10, 2017
Debt Instrument [Line Items]
Face Value	$ 3,200	$ 3,200
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(87)	(95)
Junior Subordinated Notes	$ 3,147	3,144
MetLife Inc $500M Maturing 2069 [Member]
Debt Instrument [Line Items]
Issue Date	Jul. 08, 2009
Face Value	$ 500	500
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (7)	(7)
Debt Instrument, Interest Rate, Stated Percentage	10.75%
Debt Instrument, Interest Rate Terms	LIBOR + 7.548%
Final Maturity	Aug. 01, 2069
Junior Subordinated Notes	$ 493	493
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2039-08
MetLife Capital Trust X $750M Maturing 2068 [Member]
Debt Instrument [Line Items]
Issue Date	Apr. 08, 2008
Face Value	$ 750	750	$ 750
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (11)	(11)
Debt Instrument, Interest Rate, Stated Percentage	9.25%		9.25%
Debt Instrument, Interest Rate Terms	LIBOR + 5.540%
Final Maturity	Apr. 08, 2068
Junior Subordinated Notes	$ 739	739
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2038-04
MetLife Capital Trust IV $700M Maturing 2067 [Member]
Debt Instrument [Line Items]
Issue Date	Dec. 15, 2007
Face Value	$ 700	700
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (16)	(17)
Debt Instrument, Interest Rate, Stated Percentage	7.875%
Debt Instrument, Interest Rate Terms	LIBOR + 3.960%
Final Maturity	Dec. 15, 2067
Junior Subordinated Notes	$ 684	683
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2037-12
MetLife Inc $1,250M Maturing 2066 [Member]
Debt Instrument [Line Items]
Issue Date	Dec. 19, 2006
Face Value	$ 1,250	1,250
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (19)	(21)
Debt Instrument, Interest Rate, Stated Percentage	6.40%
Debt Instrument, Interest Rate Terms	LIBOR + 2.205%
Final Maturity	Dec. 15, 2066
Junior Subordinated Notes	$ 1,231	1,229
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2036-12
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (53)	$ (56)

The expiration, mandatory redemption, or due date, month and year (YYYY-MM), of the financial instrument issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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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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Date the debt instrument was issued, in CCYY-MM-DD format.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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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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