Fair Value Disclosures - Unobservable Input Reconciliation (Details) - Level 3 - Recurring - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 6,358,451	$ 6,973,567
Purchases	832,750	160,615
Sales	0	0
Settlements	(296,870)	(244,935)
Allowance for Losses	(416)	157
Realized and unrealized (losses)/gains included in Income	(210,494)	(168,756)
Unrealized gains included in Other Comprehensive Income	(54,690)	67,285
Ending Balance	6,628,731	6,787,933
Floating rate auction-rate certificates backed by Government guaranteed student loans \| Floating Interest Rate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	19,254
Ending Balance	18,961
Floating rate auction-rate certificates backed by Government guaranteed student loans \| Floating Interest Rate \| Available-for-Sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	19,254	19,171
Purchases	0	0
Sales	0	0
Settlements	0	0
Allowance for Losses	2	(25)
Realized and unrealized (losses)/gains included in Income	0	0
Unrealized gains included in Other Comprehensive Income	(295)	0
Ending Balance	18,961	19,146
Available-for-sale securities \| Available-for-Sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	19,254	19,171
Purchases	0	0
Sales	0	0
Settlements	0	0
Allowance for Losses	2	(25)
Realized and unrealized (losses)/gains included in Income	0	0
Unrealized gains included in Other Comprehensive Income	(295)	0
Ending Balance	18,961	19,146
Farmer Mac Guaranteed Securities \| AgVantage Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,316,145
Ending Balance	6,589,224
Farmer Mac Guaranteed Securities \| Available-for-Sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,328,559	6,947,701
Purchases	832,750	160,615
Sales	0	0
Settlements	(295,663)	(243,832)
Allowance for Losses	(418)	182
Realized and unrealized (losses)/gains included in Income	(210,587)	(168,742)
Unrealized gains included in Other Comprehensive Income	(54,395)	67,285
Ending Balance	6,600,246	6,763,209
Farmer Mac Guaranteed Securities \| Available-for-Sale Securities \| AgVantage Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,316,145	6,947,701
Purchases	832,750	160,615
Sales	0	0
Settlements	(295,284)	(243,832)
Allowance for Losses	(418)	182
Realized and unrealized (losses)/gains included in Income	(210,587)	(168,742)
Unrealized gains included in Other Comprehensive Income	(53,382)	67,285
Ending Balance	6,589,224	6,763,209
Farmer Mac Guaranteed Securities \| Available-for-Sale Securities \| Farmer Mac Guaranteed USDA Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	12,414
Purchases	0
Sales	0
Settlements	(379)
Allowance for Losses	0
Realized and unrealized (losses)/gains included in Income	0
Unrealized gains included in Other Comprehensive Income	(1,013)
Ending Balance	11,022
USDA Securities:
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4,401	6,695
Purchases	0	0
Sales	0	0
Settlements	(952)	(1,103)
Allowance for Losses
Realized and unrealized (losses)/gains included in Income	(63)	(14)
Unrealized gains included in Other Comprehensive Income	0	0
Ending Balance	3,386	5,578
USDA Securities: \| Debt Securities, Trading
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4,401	6,695
Purchases	0	0
Sales	0	0
Settlements	(952)	(1,103)
Allowance for Losses	0	0
Realized and unrealized (losses)/gains included in Income	(63)	(14)
Unrealized gains included in Other Comprehensive Income	0	0
Ending Balance	3,386	$ 5,578
Guarantee and commitment obligations:
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,237
Purchases	0
Sales	0
Settlements	(255)
Allowance for Losses	0
Realized and unrealized (losses)/gains included in Income	156
Unrealized gains included in Other Comprehensive Income	0
Ending Balance	6,138
Guarantee and commitment obligations: \| Guarantee Asset
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,237
Purchases	0
Sales	0
Settlements	(255)
Allowance for Losses	0
Realized and unrealized (losses)/gains included in Income	156
Unrealized gains included in Other Comprehensive Income	0
Ending Balance	$ 6,138

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Allowance for Credit Loss

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 2
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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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