Financial Derivatives Hedged Items in Fair Value Hedging Relationships (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
HedgedItemsinFairValueHedgingRelationship [Line Items]
TotalAmountsofLineItemsPresentedintheConsolidatedStatementofIncome	$ 115,570	$ 123,814	$ 115,543
Hedged Liability Discontinued Fair Value Cumulative Increase Decrease	300
Loans [Member]
HedgedItemsinFairValueHedgingRelationship [Line Items]
Derivative, Amount of Hedged Item	194,617	149,304
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	(5,287)	(189)
Long-term Debt [Member]
HedgedItemsinFairValueHedgingRelationship [Line Items]
Derivative, Amount of Hedged Item	(2,021,356)	(1,552,935)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	8,785	5,836
Farmer Mac Guaranteed Securities:
HedgedItemsinFairValueHedgingRelationship [Line Items]
Derivative, Amount of Hedged Item	2,882,919	1,928,220
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	$ (906)	$ (22,853)

[Line Items] for HedgedItemsinFairValueHedgingRelationship [Table]

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk, remaining after discontinued hedge.

+ References

No definition available.

+ Details

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- Definition

TotalAmountsofLineItemsPresentedintheConsolidatedStatementofIncome

+ References

No definition available.

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- Definition

Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

+ References

No definition available.

+ Details

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk.

+ References

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