Fair Value Disclosures - Unobservable Input Reconciliation (Details) - Level 3 - Recurring - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 6,628,731	$ 6,787,933	$ 6,358,451	$ 6,973,567
Purchases	520,000	417,500	1,352,750	578,115
Sales	0	0	0	0
Settlements	(515,028)	(310,870)	(811,898)	(555,805)
Allowance for Losses	85	(90)	(331)	67
Realized and unrealized (losses)/gains included in Income	(149,490)	49,878	(359,984)	(118,878)
Unrealized gains/(losses) included in Other Comprehensive Income	(7,114)	(42,648)	(61,804)	24,637
Ending Balance	6,477,184	6,901,703	6,477,184	6,901,703
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	19,061		19,061
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	18,961	19,146	19,254	19,171
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Allowance for Losses	1	3	3	(22)
Realized and unrealized (losses)/gains included in Income	0	0	0	0
Unrealized gains/(losses) included in Other Comprehensive Income	99	99	(196)	99
Ending Balance	19,061	19,248	19,061	19,248
Available-for-sale securities \| Available-for-Sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	18,961	19,146	19,254	19,171
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Allowance for Losses	1	3	3	(22)
Realized and unrealized (losses)/gains included in Income	0	0	0	0
Unrealized gains/(losses) included in Other Comprehensive Income	99	99	(196)	99
Ending Balance	19,061	19,248	19,061	19,248
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	6,440,396		6,440,396
Farmer Mac Guaranteed Securities \| Available-for-Sale Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,600,246	6,763,209	6,328,559	6,947,701
Purchases	520,000	417,500	1,352,750	578,115
Sales	0	0	0	0
Settlements	(513,700)	(310,403)	(809,363)	(554,235)
Allowance for Losses	84	(93)	(334)	89
Realized and unrealized (losses)/gains included in Income	(149,205)	49,939	(359,792)	(118,803)
Unrealized gains/(losses) included in Other Comprehensive Income	(7,213)	(42,747)	(61,608)	24,538
Ending Balance	6,450,212	6,877,405	6,450,212	6,877,405
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	6,589,224	6,763,209	6,316,145	6,947,701
Purchases	520,000	417,500	1,352,750	578,115
Sales	0	0	0	0
Settlements	(513,342)	(310,403)	(808,626)	(554,235)
Allowance for Losses	84	(93)	(334)	89
Realized and unrealized (losses)/gains included in Income	(149,205)	49,939	(359,792)	(118,803)
Unrealized gains/(losses) included in Other Comprehensive Income	(6,365)	(42,747)	(59,747)	24,538
Ending Balance	6,440,396	6,877,405	6,440,396	6,877,405
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	11,022		12,414
Purchases	0		0
Sales	0		0
Settlements	(358)		(737)
Allowance for Losses	0		0
Realized and unrealized (losses)/gains included in Income	0		0
Unrealized gains/(losses) included in Other Comprehensive Income	(848)		(1,861)
Ending Balance	9,816		9,816
USDA Securities:
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,386	5,578	4,401	6,695
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(1,140)	(467)	(2,092)	(1,570)
Allowance for Losses
Realized and unrealized (losses)/gains included in Income	29	(61)	(34)	(75)
Unrealized gains/(losses) included in Other Comprehensive Income	0	0	0	0
Ending Balance	2,275	5,050	2,275	5,050
USDA Securities: \| Debt Securities, Trading
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3,386	5,578	4,401	6,695
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(1,140)	(467)	(2,092)	(1,570)
Allowance for Losses	0	0	0	0
Realized and unrealized (losses)/gains included in Income	29	(61)	(34)	(75)
Unrealized gains/(losses) included in Other Comprehensive Income	0	0	0	0
Ending Balance	2,275	$ 5,050	2,275	$ 5,050
Guarantee and commitment obligations:
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,138		6,237
Purchases	0		0
Sales	0		0
Settlements	(188)		(443)
Allowance for Losses	0		0
Realized and unrealized (losses)/gains included in Income	(314)		(158)
Unrealized gains/(losses) included in Other Comprehensive Income	0		0
Ending Balance	5,636		5,636
Guarantee and commitment obligations: \| Guarantee Asset
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,138		6,237
Purchases	0		0
Sales	0		0
Settlements	(188)		(443)
Allowance for Losses	0		0
Realized and unrealized (losses)/gains included in Income	(314)		(158)
Unrealized gains/(losses) included in Other Comprehensive Income	0		0
Ending Balance	$ 5,636		$ 5,636

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

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- Definition

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 https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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- Definition

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
-Subparagraph (c)(1a)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-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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-SubTopic 10
-Section 50
-Paragraph 2
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