| Cover Page | Jan. 16, 2020 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 16, 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 [Member] | |
| 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 [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Class C non-voting common stock |
| Trading Symbol | AGM |
| Security Exchange Name | NYSE |
| Series A Preferred Stock [Member] | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 5.875% Non-Cumulative Preferred Stock, Series A |
| Trading Symbol | AGM.PRA |
| Security Exchange Name | NYSE |
| Series C Preferred Stock [Member] | |
| 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 [Member] | |
| 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 |
