| Cover Page | Dec. 22, 2020 | Nov. 18, 2020 |
| Entity Information [Line Items] | ||
| Document Type | 8-K | |
| Document Period End Date | Dec. 22, 2020 | |
| Entity Registrant Name | FEDERAL AGRICULTURAL MORTGAGE CORPORATION | |
| City Area Code | 202 | |
| Local Phone Number | 872-7700 | |
| Written Communications | false | |
| Soliciting Material | false | |
| Pre-commencement Tender Offer | false | |
| Pre-commencement Issuer Tender Offer | false | |
| Entity File Number | 001-14951 | |
| Entity Central Index Key | 0000845877 | |
| Entity Tax Identification Number | 52-1578738 | |
| Entity Address, Address Line One | 1999 K Street, N.W., 4th Floor, | |
| Entity Address, Postal Zip Code | 20006 | |
| Amendment Flag | false | |
| Entity Incorporation, State or Country Code | X1 | |
| Entity Address, City or Town | Washington, | |
| Entity Address, State or Province | DC | |
| Entity Emerging Growth Company | false | |
| Common Class A | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | Class A voting common stock | |
| Trading Symbol | AGM.A | |
| Security Exchange Name | NYSE | |
| Common Class C | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | Class C non-voting common stock | |
| Trading Symbol | AGM | |
| Security Exchange Name | NYSE | |
| Series C Preferred Stock | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | 6.000% Fixed-to-Floating Rate Non-Cumulative Preferred Stock, Series C | |
| Trading Symbol | AGM.PRC | |
| Security Exchange Name | NYSE | |
| Series D Preferred Stock | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | 5.700% Non-Cumulative Preferred Stock, Series D | |
| Trading Symbol | AGM.PRD | |
| Security Exchange Name | NYSE | |
| Series E Preferred Stock | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | 5.750% Non-Cumulative Preferred Stock, Series E | |
| Trading Symbol | AGM.PRE | |
| Security Exchange Name | NYSE | |
| Series F Preferred Stock | ||
| Entity Information [Line Items] | ||
| Title of 12(b) Security | 5.250% Non-Cumulative Preferred Stock, Series F | |
| Trading Symbol | AGM.PRF | |
| Security Exchange Name | NYSE |
