COVER PAGE - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 03, 2020	Jun. 30, 2019
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-14951
Entity Registrant Name	FEDERAL AGRICULTURAL MORTGAGE CORPORATION
Entity Incorporation, State or Country Code	X1
Entity Tax Identification Number	52-1578738
Entity Address, Address Line One	1999 K Street, N.W., 4th Floor,
Entity Address, City or Town	Washington,
Entity Address, State or Province	DC
Entity Address, Postal Zip Code	20006
City Area Code	(202)
Local Phone Number	872-7700
Title of 12(g) Security	Class B voting common stock
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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 Shell Company	false
Entity Public Float			$ 639,482,137
Documents Incorporated by Reference	The definitive proxy statement relating to the registrant's 2020 Annual Meeting of Stockholders (portions of which are incorporated by reference into Part III of this Annual Report on Form 10-K)
Entity Central Index Key	0000845877
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Class A voting common stock
Entity Information [Line Items]
Title of 12(b) Security	Class A voting common stock
Trading Symbol	AGM.A
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		1,030,780
Common Class B, Voting
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		500,301
Class C non-voting common stock
Entity Information [Line Items]
Title of 12(b) Security	Class C non-voting common stock
Trading Symbol	AGM
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		9,180,969
5.875% Non-Cumulative Preferred Stock, Series A
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
6.000% Fixed-to-Floating Rate Non-Cumulative Preferred Stock, Series C
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
5.700% Non-Cumulative Preferred Stock, Series D
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