| Document and Entity Information | May 16, 2022 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | METLIFE INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001099219 |
| Document Type | 8-K |
| Document Period End Date | May 16, 2022 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-15787 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, par value $0.01 |
| Trading Symbol | MET |
| Security Exchange Name | NYSE |
| Series A Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Floating Rate Non-Cumulative Preferred Stock,Series A, par value $0.01 |
| Trading Symbol | MET PRA |
| Security Exchange Name | NYSE |
| Series E Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Depositary Shares, each representing a 1/1,000th interest in a share of 5.625% Non-CumulativePreferred Stock, Series E |
| Trading Symbol | MET PRE |
| Security Exchange Name | NYSE |
| Series F Preferred Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Depositary Shares, each representing a 1/1,000th interest in a share of 4.75% Non-CumulativePreferred Stock, Series F |
| Trading Symbol | MET PRF |
| Security Exchange Name | NYSE |
