Farmer Mac Guaranteed Securities and USDA Securities - Farmer Mac Guaranteed Securities and USDA Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2018	Dec. 31, 2019
Held-to-maturity:
Allowance for losses	$ (640)
Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unpaid Principal Balance	3,682,587		$ 3,638,142
Amortized Cost	3,718,134		3,679,611
Allowance for losses	(600)
Unrealized Gains	100,339		70,495
Unrealized Losses	(1,637)		(922)
Fair Value	3,816,196
Fair Value	3,816,836		3,749,184
Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance	1,448,560		1,447,471
Amortized Cost	1,448,523		1,447,451
Allowance for losses	(640)
Unrealized Gains	32,173		16,139
Unrealized Losses	0		(164)
Fair Value	1,480,056
Fair Value			1,463,426
Available-for-sale:
Amortized Cost	7,273,303
Fair Value	7,587,352
USDA Securities:
Trading:
Fair Value	8,408		8,913
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unamortized Premium/(Discount)	35,547		41,469
Available-for-sale:
Unamortized Premium/(Discount)	35,547		41,469
Trading:
Unamortized Premium/(Discount)	35,547		41,469
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	(37)		(20)
Available-for-sale:
Unamortized Premium/(Discount)	(37)		(20)
Trading:
Unamortized Premium/(Discount)	(37)		(20)
Institutional Credit
Trading:
Available-for-sale, accrued interest excluded	35,900
Held-to-maturity, accrued interest excluded	40,600
Trading securities, accrued interest excluded	200
Institutional Credit \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance	1,415,120		1,415,584
Amortized Cost	1,415,010		1,415,410
Allowance for losses	(640)
Unrealized Gains	31,294		15,300
Unrealized Losses	0		(164)
Fair Value	1,445,664
Fair Value			1,430,546
Available-for-sale:
Unpaid Principal Balance	7,273,414		7,017,095
Amortized Cost	7,273,303		7,016,971
Allowance for losses	(166)
Unrealized Gains	378,974		161,316
Unrealized Losses	(64,925)		(35,262)
Fair Value	7,587,186		7,143,025
Institutional Credit \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	(110)		(174)
Available-for-sale:
Unamortized Premium/(Discount)	(110)		(174)
Trading:
Unamortized Premium/(Discount)	(110)		(174)
Institutional Credit \| Available-for-Sale Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	(111)		(124)
Available-for-sale:
Unamortized Premium/(Discount)	(111)		(124)
Trading:
Unamortized Premium/(Discount)	(111)		(124)
USDA Guarantees
Held-to-maturity:
Unamortized Premium/(Discount)	(100)		200
Available-for-sale:
Unamortized Premium/(Discount)	(100)		200
Trading:
Unamortized Premium/(Discount)	(100)		200
USDA Guarantees \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance	33,440		31,887
Amortized Cost	33,513		32,041
Allowance for losses	0
Unrealized Gains	879		839
Unrealized Losses	0		0
Fair Value	34,392
Fair Value			32,880
USDA Guarantees \| USDA Securities:
Held-to-maturity:
Unpaid Principal Balance	2,234,027		2,190,671
Amortized Cost	2,269,611		2,232,160
Allowance for losses	0
Unrealized Gains	68,166		54,356
Unrealized Losses	(1,637)		(758)
Fair Value	2,336,140
Fair Value			2,285,758
Trading:
Unpaid Principal Balance	7,835		8,400
Amortized Cost	8,268		8,879
Allowance for losses	0
Unrealized Gains	149	$ 61
Unrealized Losses	(9)	$ (27)
Fair Value	$ 8,408		$ 8,913
Trading securities, weighted-average yield	5.19%		5.20%
USDA Guarantees \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)	$ 73		$ 154
Available-for-sale:
Unamortized Premium/(Discount)	73		154
Trading:
Unamortized Premium/(Discount)	73		154
USDA Guarantees \| Held-to-Maturity Securities \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)	35,584		41,489
Available-for-sale:
Unamortized Premium/(Discount)	35,584		41,489
Trading:
Unamortized Premium/(Discount)	35,584		41,489
USDA Guarantees \| Trading Securities \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)	433		479
Available-for-sale:
Unamortized Premium/(Discount)	433		479
Trading:
Unamortized Premium/(Discount)	$ 433		$ 479

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