Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	Apr. 29, 2022
Entity Information [Line Items]
Document Type	10-Q
Entity Registrant Name	MetLife, Inc.
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-15787
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-4075851
Entity Address, Address Line One	200 Park Avenue,
Entity Address, City or Town	New York,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10166-0188
City Area Code	212
Local Phone Number	578-9500
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001099219
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		813,205,926
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01
Trading Symbol	MET
Security Exchange Name	NYSE
Floating Rate Non-Cumulative Preferred Stock, Series A, par value $0.01
Entity Information [Line Items]
Title of 12(b) Security	Floating Rate Non-Cumulative Preferred Stock, Series A, par value $0.01
Trading Symbol	MET PRA
Security Exchange Name	NYSE
Depositary Shares, each representing a 1/1,000th interest in a share of 5.625% Non-Cumulative Preferred Stock, Series E
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,000th interest in a share of 5.625% Non-Cumulative Preferred Stock, Series E
Trading Symbol	MET PRE
Security Exchange Name	NYSE
Depositary Shares, each representing a 1/1,000th interest in a share of 4.75% Non-Cumulative Preferred Stock, Series F
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,000th interest ina share of 4.75% Non-Cumulative Preferred Stock, Series F
Trading Symbol	MET PRF
Security Exchange Name	NYSE