Junior Subordinated Debt Securities (Junior Subordinated Debt Securities) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Feb. 10, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Face Value	$ 3,200		$ 3,200
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(95)		(103)
Junior Subordinated Notes	$ 3,144		3,169
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)		(4)
Debt Instrument, Interest Rate, Stated Percentage	10.75%
Debt Instrument, Description of Variable Rate Basis	LIBOR + 7.548%
Final Maturity	Aug. 01, 2069
Junior Subordinated Notes	$ 493		496
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2039-08
Debt Instrument, Basis Spread on Variable Rate	7.548%
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)		(6)
Debt Instrument, Interest Rate, Stated Percentage	9.25%	9.25%
Debt Instrument, Description of Variable Rate Basis	LIBOR + 5.540%
Final Maturity	Apr. 08, 2068
Junior Subordinated Notes	$ 739		744
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2038-04
Debt Instrument, Basis Spread on Variable Rate	5.54%
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	$ (17)		(10)
Debt Instrument, Interest Rate, Stated Percentage	7.875%
Debt Instrument, Description of Variable Rate Basis	LIBOR + 3.960%
Final Maturity	Dec. 15, 2067
Junior Subordinated Notes	$ 683		690
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2037-12
Debt Instrument, Basis Spread on Variable Rate	3.96%
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	$ (21)		(11)
Debt Instrument, Interest Rate, Stated Percentage	6.40%
Debt Instrument, Description of Variable Rate Basis	LIBOR + 2.205%
Final Maturity	Dec. 15, 2066
Junior Subordinated Notes	$ 1,229		1,239
Debt Conversion, Converted Instrument, Expiration or Due Date, Month and Year	2036-12
Debt Instrument, Basis Spread on Variable Rate	2.205%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ (56)		$ (31)

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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- Definition

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

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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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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