Related Party Transactions - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Commitment fees receivable	$ 100,000	$ 100,000
Zions Bancorporation, National Association
Related Party Transaction [Line Items]
Related party percent of Farmer Mac's outstanding business volume	3.40%	4.10%
Servicing fees	$ 11,000,000	$ 11,800,000	$ 12,200,000
CFC
Related Party Transaction [Line Items]
Transaction with related party, percent of volume	18.40%	9.50%	12.50%
Related party percent of Farmer Mac's outstanding business volume	19.50%	19.20%
Servicing fees	$ 3,300,000	$ 3,300,000	$ 3,200,000
Interest receivables	7,800,000	5,300,000
Interest income	50,000,000	63,100,000	97,300,000
Commitment fees earned	1,200,000	1,300,000	1,700,000
CoBank
Related Party Transaction [Line Items]
Servicing fees	3,200,000	2,300,000	1,200,000
AgFirst Farm Credit Bank
Related Party Transaction [Line Items]
Commitment fees receivable	100,000	100,000
Commitment fees earned	1,200,000	1,200,000	1,200,000
Guarantee fees	19,000	25,000	29,000
AgFirst Farm Credit Bank | Guarantee Obligations
Related Party Transaction [Line Items]
Unpaid principal balance	11,000,000	32,500,000	26,700,000
Outstanding balance	363,900,000	331,200,000
AgFirst Farm Credit Bank | Performance Guarantee
Related Party Transaction [Line Items]
Outstanding balance	4,000,000	5,500,000
Farm Credit Bank of Texas
Related Party Transaction [Line Items]
Servicing fees	100,000	100,000	100,000
Commitment fees earned	1,900,000	1,200,000	$ 1,100,000
Farm Credit Bank of Texas | Guarantee Obligations
Related Party Transaction [Line Items]
Outstanding balance	$ 625,600,000	$ 304,900,000
Class A voting common stock | Zions Bancorporation, National Association
Related Party Transaction [Line Items]
Ownership by a related party	31.20%
Class A voting common stock | CFC
Related Party Transaction [Line Items]
Ownership by a related party	7.90%
Common Class B | CoBank
Related Party Transaction [Line Items]
Ownership by a related party	32.60%
Common Class B | AgFirst Farm Credit Bank
Related Party Transaction [Line Items]
Ownership by a related party	16.80%
Common Class B | Farm Credit Bank of Texas
Related Party Transaction [Line Items]
Ownership by a related party	7.70%
Agricultural Finance | Zions Bancorporation, National Association
Related Party Transaction [Line Items]
Transaction with related party, percent of volume of loan purchases	8.00%	7.10%	9.50%
Transaction with related party, percent of volume	5.60%	6.20%	7.60%
USDA Guarantee | Zions Bancorporation, National Association
Related Party Transaction [Line Items]
Transaction with related party, percent of volume	2.10%	1.40%	2.10%
Rural  Utilities | CFC
Related Party Transaction [Line Items]
Transaction with related party, percent of volume of loan purchases	36.90%	36.70%	9.80%
Rural  Utilities | CoBank
Related Party Transaction [Line Items]
Transaction with related party, percent of volume of loan purchases	60.20%	56.00%	89.10%
AgVantage Securities | CFC
Related Party Transaction [Line Items]
Transaction with related party, percent of volume	37.00%	19.20%	25.50%
AgVantage Securities | CFC | Guarantee Obligations
Related Party Transaction [Line Items]
Unpaid principal balance	$ 1,450,000,000	$ 250,000,000	$ 575,000,000
Mortgages | Agricultural Finance | Bath State Bank
Related Party Transaction [Line Items]
Unpaid principal balance	5,000,000
Mortgages | Agricultural Finance | Farm Credit of Florida [Member]
Related Party Transaction [Line Items]
Unpaid principal balance	1,100,000	200,000	0
Mortgages | Rural  Utilities
Related Party Transaction [Line Items]
Unpaid principal balance	$ 207,500,000	$ 416,800,000	776,400,000
Unfunded Loan Commitment | CoBank
Related Party Transaction [Line Items]
Transaction with related party, percent of volume of loan purchases	5.60%	5.10%
Unfunded commitments	$ 72,000,000
USDA Securities: | USDA Guarantee | Zions Bancorporation, National Association
Related Party Transaction [Line Items]
Unpaid principal balance	9,565,000	$ 10,764,000	8,875,000
USDA Securities: | USDA Guarantee | Bath State Bank
Related Party Transaction [Line Items]
Unpaid principal balance	$ 2,300,000	$ 9,200,000	$ 4,000,000