Farmer Mac Guaranteed Securities and USDA Securities - Schedule of On-Balance Sheet Securities (Details) - USD ($) $ in Thousands		12 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance	$ 2,248,451	$ 1,175,886
Amortized Cost	2,248,476	1,175,912
Allowance for losses	(173)	(120)
Unrealized Gains	14,562	25,259
Unrealized Losses	(8,134)	(61)
Fair Value	2,254,731	1,200,990
Available-for-sale:
Amortized cost	5,909,989
USDA Securities:
Trading:
Fair Value	4,793	6,695
Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unpaid Principal Balance	4,678,401	3,622,436
Amortized Cost	4,705,693	3,649,538
Allowance for losses	(173)	(120)
Unrealized Gains	101,550	183,007
Unrealized Losses	(8,925)	(621)
Fair Value	4,798,145	3,831,804
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	25	26
Available-for-sale:
Unamortized Premium/(Discount)	25	26
Trading:
Unamortized Premium/(Discount)	25	26
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unamortized Premium/(Discount)	27,292	27,102
Available-for-sale:
Unamortized Premium/(Discount)	27,292	27,102
Trading:
Unamortized Premium/(Discount)	27,292	27,102
USDA Guarantees
Held-to-maturity:
Unamortized Premium/(Discount)		100
Available-for-sale:
Unamortized Premium/(Discount)		100
Trading:
Unamortized Premium/(Discount)		100
USDA Guarantees \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance	28,227	34,456
Amortized Cost	28,265	34,537
Allowance for losses	0	0
Unrealized Gains	936	1,273
Unrealized Losses	0	0
Fair Value	29,201	35,810
USDA Guarantees \| USDA Securities:
Held-to-maturity:
Unpaid Principal Balance	2,429,950	2,446,550
Amortized Cost	2,457,217	2,473,626
Allowance for losses	0	0
Unrealized Gains	86,988	157,748
Unrealized Losses	(791)	(560)
Fair Value	2,543,414	2,630,814
Trading:
Unpaid Principal Balance	4,632	6,413
Amortized Cost	4,747	6,611
Allowance for losses	0	0
Unrealized Gains	48	84
Unrealized Losses	(2)	0
Fair Value	$ 4,793	$ 6,695
Trading securities, weighted-average yield	5.13%	5.05%
USDA Guarantees \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	$ 38	$ 81
Available-for-sale:
Unamortized Premium/(Discount)	38	81
Trading:
Unamortized Premium/(Discount)	38	81
USDA Guarantees \| Held-to-Maturity Securities \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)	27,267	27,076
Available-for-sale:
Unamortized Premium/(Discount)	27,267	27,076
Trading:
Unamortized Premium/(Discount)	27,267	27,076
USDA Guarantees \| Trading \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)	115	198
Available-for-sale:
Unamortized Premium/(Discount)	115	198
Trading:
Unamortized Premium/(Discount)	115	198
AgVantage Securities
Trading:
Available-for-sale, accrued interest excluded	30,400	32,300
Held-to-maturity, accrued interest excluded	37,500	44,700
Trading securities, accrued interest excluded	100	200
AgVantage Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance	2,220,224	1,141,430
Amortized Cost	2,220,211	1,141,375
Allowance for losses	(173)	(120)
Unrealized Gains	13,626	23,986
Unrealized Losses	(8,134)	(61)
Fair Value	2,225,530	1,165,180
Available-for-sale:
Unpaid Principal Balance	5,908,666	6,593,518
Amortized cost	5,909,989	6,594,992
Allowance for losses	(290)	(310)
Unrealized Gains	245,361	368,257
Unrealized Losses	(16,301)	(15,238)
Fair Value	6,138,759
AgVantage Securities \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	(13)	(55)
Available-for-sale:
Unamortized Premium/(Discount)	(13)	(55)
Trading:
Unamortized Premium/(Discount)	(13)	(55)
AgVantage Securities \| Available-for-Sale Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	1,323	1,474
Available-for-sale:
Unamortized Premium/(Discount)	1,323	1,474
Trading:
Unamortized Premium/(Discount)	$ 1,323	$ 1,474

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