Related Party Transactions - Zions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Common Stock Ownership Percentage by a Related Party	5.00%
Derivative, Notional Amount	$ 6,837,571invest_DerivativeNotionalAmount	$ 6,691,851invest_DerivativeNotionalAmount
Accrued interest payable (includes $5,145 and $2,823, respectively, related to consolidated trusts)	48,355	53,772
Zions First National Bank [Member]
Related Party Transaction [Line Items]
Related Party's percent of Farmer Mac Total Outstanding Book of Business	5.90%	5.10%
Related Party Transaction, Expenses from Transactions with Related Party	8,400	7,000	6,500
Accrued interest payable (includes $5,145 and $2,823, respectively, related to consolidated trusts)		300
Zions First National Bank [Member] \| Derivative [Member]
Related Party Transaction [Line Items]
Derivative, Notional Amount	0	29,300
Zions First National Bank [Member] \| Medium-term Notes [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	5,000	0	0
Zions First National Bank [Member] \| Sale of Farmer Mac Guaranteed Securities [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	147,234	120,409	5,327
Common Class A, Voting [Member] \| Zions First National Bank [Member]
Related Party Transaction [Line Items]
Common Stock Ownership Percentage by a Related Party	31.20%
Farm & Ranch [Member] \| Zions First National Bank [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Related Party's Percent of Total Program Loans	22.30%	25.50%	29.60%
Related Party Transaction, Related Party's percent of total Program	14.60%	15.40%	12.80%
USDA Guarantee [Member] \| Zions First National Bank [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Related Party's percent of total Program	12.40%	3.60%	3.00%
Loans Collateralized by Real Estate [Member] \| Farm & Ranch [Member] \| Zions First National Bank [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	155,808	210,088	168,826
USDA Securities [Member] \| USDA Guarantee [Member] \| Zions First National Bank [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	42,637	13,153	14,415
On-balance sheet [Member] \| Farmer Mac Guaranteed Securities [Member] \| Institutional Credit [Member] \| Zions First National Bank [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Purchases from Related Party	$ 50,237	$ 0	$ 0

Common Stock Ownership Percentage by a Related Party

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- Definition

Related Party's percent of Farmer Mac Total Outstanding Book of Business

+ References

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Related Party Transaction, Related Party's percent of total Program

+ References

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Related Party Transaction, Related Party's Percent of Total Program Loans

+ References

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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Amount of interest payable on debt, including, but not limited to, trade payables.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

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-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.15(a))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph a

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 5

-Article 9

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Amount of transactions with related party during the financial reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

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- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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- Definition

Purchases during the period (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

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