Farmer Mac Guaranteed Securities and USDA Securities - Schedule of On-Balance Sheet Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2020
Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance		$ 1,447,471	$ 1,175,886
Amortized Cost		1,447,451	1,175,912
Allowance for losses			(120)
Unrealized Gains		16,139	25,259
Unrealized Losses		(164)	(61)
Fair Value			1,200,990
Fair Value		1,463,426
Available-for-sale:
Amortized cost of available-for-sale investment securities			6,594,992
Carrying value			6,947,701
USDA Securities:
Trading:
Fair Value		8,913	6,695
Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unpaid Principal Balance		3,638,142	3,622,436
Amortized Cost		3,679,611	3,649,538
Allowance for losses			(120)
Unrealized Gains		70,495	183,007
Unrealized Losses		(922)	(621)
Fair Value			3,831,804
Fair Value		3,749,184	3,831,804
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		(20)	26
Available-for-sale:
Unamortized Premium/(Discount)		(20)	26
Trading:
Unamortized Premium/(Discount)		(20)	26
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unamortized Premium/(Discount)		41,469	27,102
Available-for-sale:
Unamortized Premium/(Discount)		41,469	27,102
Trading:
Unamortized Premium/(Discount)		41,469	27,102
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	34,456
Amortized Cost		32,041	34,537
Allowance for losses			0
Unrealized Gains		839	1,273
Unrealized Losses		0	0
Fair Value			35,810
Fair Value		32,880
USDA Guarantees \| USDA Securities:
Held-to-maturity:
Unpaid Principal Balance		2,190,671	2,446,550
Amortized Cost		2,232,160	2,473,626
Allowance for losses			0
Unrealized Gains		54,356	157,748
Unrealized Losses		(758)	(560)
Fair Value			2,630,814
Fair Value		2,285,758
Trading:
Unpaid Principal Balance		8,400	6,413
Amortized Cost		8,879	6,611
Allowance for losses			0
Unrealized Gains	$ 84	61
Unrealized Losses	$ 0	(27)
Fair Value		$ 8,913	$ 6,695
Trading securities, weighted-average yield		5.20%	5.05%
USDA Guarantees \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		$ 154	$ 81
Available-for-sale:
Unamortized Premium/(Discount)		154	81
Trading:
Unamortized Premium/(Discount)		154	81
USDA Guarantees \| Held-to-Maturity Securities \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)		41,489	27,076
Available-for-sale:
Unamortized Premium/(Discount)		41,489	27,076
Trading:
Unamortized Premium/(Discount)		41,489	27,076
USDA Guarantees \| Trading \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)		479	198
Available-for-sale:
Unamortized Premium/(Discount)		479	198
Trading:
Unamortized Premium/(Discount)		479	198
AgVantage Securities
Trading:
Available-for-sale, accrued interest excluded			32,300
Held-to-maturity, accrued interest excluded			44,700
Trading securities, accrued interest excluded			200
AgVantage Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance		1,415,584	1,141,430
Amortized Cost		1,415,410	1,141,375
Allowance for losses			(120)
Unrealized Gains		15,300	23,986
Unrealized Losses		(164)	(61)
Fair Value			1,165,180
Fair Value		1,430,546
Available-for-sale:
Unpaid Principal Balance		7,017,095	6,593,518
Amortized cost of available-for-sale investment securities		7,016,971	6,594,992
Allowance for losses			(310)
Unrealized Gains		161,316	368,257
Unrealized Losses		(35,262)	(15,238)
Carrying value		7,143,025	6,947,701
AgVantage Securities \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		(174)	(55)
Available-for-sale:
Unamortized Premium/(Discount)		(174)	(55)
Trading:
Unamortized Premium/(Discount)		(174)	(55)
AgVantage Securities \| Available-for-Sale Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)		(124)	1,474
Available-for-sale:
Unamortized Premium/(Discount)		(124)	1,474
Trading:
Unamortized Premium/(Discount)		$ (124)	$ 1,474

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