Farmer Mac Guaranteed Securities and USDA Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2020
Held-to-maturity:
Allowance for losses			$ (216)
Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unpaid Principal Balance		$ 3,638,142	3,582,183
Amortized Cost		3,679,611	3,611,634
Unrealized Gains		70,495	132,716
Unrealized Losses		(922)	(1,498)
Fair Value			3,742,636
Fair Value		3,749,184	3,742,636
Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance		1,447,471	1,200,767
Amortized Cost		1,447,451	1,200,786
Allowance for losses			(216)
Unrealized Gains		16,139	26,995
Unrealized Losses		(164)	(100)
Fair Value			1,227,465
Fair Value		1,463,426
Available-for-sale:
Amortized Cost			7,150,606
Carrying value			7,511,638
USDA Securities:
Trading:
Fair Value		8,913	6,830
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unamortized Premium/(Discount)		41,469	29,451
Available-for-sale:
Unamortized Premium/(Discount)		41,469	29,451
Trading:
Unamortized Premium/(Discount)		41,469	29,451
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		(20)	19
Available-for-sale:
Unamortized Premium/(Discount)		(20)	19
Trading:
Unamortized Premium/(Discount)		(20)	19
AgVantage Securities
Trading:
Available-for-sale, accrued interest excluded			32,700
Held-to-maturity, accrued interest excluded			41,100
Trading securities, accrued interest excluded			100
AgVantage Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance		1,415,584	1,164,353
Amortized Cost		1,415,410	1,164,280
Allowance for losses			(216)
Unrealized Gains		15,300	25,969
Unrealized Losses		(164)	(99)
Fair Value			1,189,934
Fair Value		1,430,546
Available-for-sale:
Unpaid Principal Balance		7,017,095	7,149,082
Amortized Cost		7,016,971	7,150,606
Allowance for losses			(330)
Unrealized Gains		161,316	394,280
Unrealized Losses		(35,262)	(32,918)
Carrying value		7,143,025	7,511,638
AgVantage Securities \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		(174)	(73)
Available-for-sale:
Unamortized Premium/(Discount)		(174)	(73)
Trading:
Unamortized Premium/(Discount)		(174)	(73)
AgVantage Securities \| Available-for-Sale Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		(124)	1,524
Available-for-sale:
Unamortized Premium/(Discount)		(124)	1,524
Trading:
Unamortized Premium/(Discount)		(124)	1,524
USDA Guarantees
Held-to-maturity:
Unamortized Premium/(Discount)		(200)	(100)
Available-for-sale:
Unamortized Premium/(Discount)		(200)	(100)
Trading:
Unamortized Premium/(Discount)		(200)	(100)
USDA Guarantees \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance		31,887	36,414
Amortized Cost		32,041	36,506
Allowance for losses			0
Unrealized Gains		839	1,026
Unrealized Losses		0	(1)
Fair Value			37,531
Fair Value		32,880
USDA Guarantees \| USDA Securities:
Held-to-maturity:
Unpaid Principal Balance		2,190,671	2,381,416
Amortized Cost		2,232,160	2,410,848
Allowance for losses			0
Unrealized Gains		54,356	105,721
Unrealized Losses		(758)	(1,398)
Fair Value			2,515,171
Fair Value		2,285,758
Trading:
Unpaid Principal Balance		8,400	6,617
Amortized Cost		8,879	6,969
Allowance for losses			0
Unrealized Gains	$ 10	61
Unrealized Losses	$ (149)	(27)
Fair Value		$ 8,913	$ 6,830
Trading securities, weighted-average yield		5.20%	5.09%
USDA Guarantees \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		$ 154	$ 92
Available-for-sale:
Unamortized Premium/(Discount)		154	92
Trading:
Unamortized Premium/(Discount)		154	92
USDA Guarantees \| Held-to-Maturity Securities \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)		41,489	29,432
Available-for-sale:
Unamortized Premium/(Discount)		41,489	29,432
Trading:
Unamortized Premium/(Discount)		41,489	29,432
USDA Guarantees \| Trading Securities \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)		479	352
Available-for-sale:
Unamortized Premium/(Discount)		479	352
Trading:
Unamortized Premium/(Discount)		$ 479	$ 352

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