Farmer Mac Guaranteed Securities and USDA Securities - Farmer Mac Guaranteed Securities and USDA Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Farmer Mac Guaranteed Securities and USDA Securities [Member]
Held-to-maturity:
Unpaid Principal Balance	$ 4,112,824	$ 4,207,531
Amortized Cost	4,165,727	4,262,792
Unrealized Gains	7,273	2,735
Unrealized Losses	(27,341)	(74,175)
Fair Value	4,145,659	4,191,352
Farmer Mac Guaranteed Securities [Member]
Held-to-maturity:
Unpaid Principal Balance	2,040,413	2,096,568
Amortized Cost	2,040,415	2,096,618
Unrealized Gains	7,272	2,735
Unrealized Losses	(5,932)	(11,948)
Fair Value	2,041,755	2,087,405
Available-for-sale:
Amortized Cost	6,408,128
Fair Value	6,441,624
USDA Securities [Member]
Trading:
Fair Value	9,487	9,999
Held-to-maturity Securities [Member] \| Farmer Mac Guaranteed Securities and USDA Securities [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	52,903	55,261
Available-for-sale:
Unamortized Premium/(Discount)	52,903	55,261
Trading:
Unamortized Premium/(Discount)	52,903	55,261
Held-to-maturity Securities [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	2	50
Available-for-sale:
Unamortized Premium/(Discount)	2	50
Trading:
Unamortized Premium/(Discount)	2	50
Institutional Credit [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-maturity:
Unpaid Principal Balance	2,013,619	2,069,185
Amortized Cost	2,013,384	2,068,991
Unrealized Gains	7,035	2,637
Unrealized Losses	(5,932)	(11,948)
Fair Value	2,014,487	2,059,680
Available-for-sale:
Unpaid Principal Balance	6,408,318	6,003,733
Amortized Cost	6,408,128	6,003,529
Unrealized Gains	67,066	22,335
Unrealized Losses	(33,570)	(51,367)
Fair Value	6,441,624	5,974,497
Institutional Credit [Member] \| Held-to-maturity Securities [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	(235)	(194)
Available-for-sale:
Unamortized Premium/(Discount)	(235)	(194)
Trading:
Unamortized Premium/(Discount)	(235)	(194)
Institutional Credit [Member] \| Available-for-sale Securities [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	(190)	(204)
Available-for-sale:
Unamortized Premium/(Discount)	(190)	(204)
Trading:
Unamortized Premium/(Discount)	(190)	(204)
USDA Guarantees [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	(200)	(200)
Available-for-sale:
Unamortized Premium/(Discount)	(200)	(200)
Trading:
Unamortized Premium/(Discount)	(200)	(200)
USDA Guarantees [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-maturity:
Unpaid Principal Balance	26,794	27,383
Amortized Cost	27,031	27,627
Unrealized Gains	237	98
Unrealized Losses	0	0
Fair Value	27,268	27,725
USDA Guarantees [Member] \| USDA Securities [Member]
Held-to-maturity:
Unpaid Principal Balance	2,072,411	2,110,963
Amortized Cost	2,125,312	2,166,174
Unrealized Gains	1	0
Unrealized Losses	(21,409)	(62,227)
Fair Value	2,103,904	2,103,947
Trading:
Unpaid Principal Balance	9,087	9,591
Amortized Cost	9,736	10,292
Unrealized Gains	22	20
Unrealized Losses	(271)	(313)
Fair Value	$ 9,487	$ 9,999
Trading securities, weighted-average yield	5.23%	5.21%
USDA Guarantees [Member] \| Held-to-maturity Securities [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	$ 237	$ 244
Available-for-sale:
Unamortized Premium/(Discount)	237	244
Trading:
Unamortized Premium/(Discount)	237	244
USDA Guarantees [Member] \| Held-to-maturity Securities [Member] \| USDA Securities [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	52,901	55,211
Available-for-sale:
Unamortized Premium/(Discount)	52,901	55,211
Trading:
Unamortized Premium/(Discount)	52,901	55,211
USDA Guarantees [Member] \| Trading Securities [Member] \| USDA Securities [Member]
Held-to-maturity:
Unamortized Premium/(Discount)	649	701
Available-for-sale:
Unamortized Premium/(Discount)	649	701
Trading:
Unamortized Premium/(Discount)	$ 649	$ 701

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