Fair Value Disclosures - Summary of Carrying Value and Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial derivatives	$ 8,007	$ 7,093
Guarantee and commitment fees receivable:	40,178	39,895
Derivative Liability	(29,000)	1,673
Guarantee and commitment obligation	38,597	38,400
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	436,152	302,022
Loans	5,360,900	5,266,786
Financial derivatives	8,007	7,093
Debt securities of consolidated trusts held by third parties	1,486,733	1,404,945
Derivative Liability	17,841	26,599
Reported Value Measurement [Member] \| Investment Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	2,269,034	2,260,437
Reported Value Measurement [Member] \| Farmer Mac Guaranteed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	8,024,611	7,598,188
Reported Value Measurement [Member] \| USDA Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	2,154,111	2,131,365
Reported Value Measurement [Member] \| Long-Term Standby Purchase Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable:	36,436	35,718
Guarantee and commitment obligation	35,468	34,824
Reported Value Measurement [Member] \| Farmer Mac Guaranteed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable:	3,742	4,177
Guarantee and commitment obligation	3,129	3,576
Reported Value Measurement [Member] \| Due within one year [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable:	7,378,927	8,089,826
Reported Value Measurement [Member] \| Long-term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable:	8,419,424	7,432,790
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	436,152	302,022
Loans	5,331,095	5,279,225
Financial derivatives	8,007	7,093
Debt securities of consolidated trusts held by third parties	1,451,781	1,386,652
Derivative Liability	17,841	26,599
Estimate of Fair Value Measurement [Member] \| Investment Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	2,269,877	2,260,969
Estimate of Fair Value Measurement [Member] \| Farmer Mac Guaranteed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	8,002,686	7,588,806
Estimate of Fair Value Measurement [Member] \| USDA Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable Securities	2,067,583	2,076,396
Estimate of Fair Value Measurement [Member] \| Long-Term Standby Purchase Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable:	37,764	33,871
Guarantee and commitment obligation	36,796	32,976
Estimate of Fair Value Measurement [Member] \| Farmer Mac Guaranteed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Guarantee and commitment fees receivable:	3,710	4,323
Guarantee and commitment obligation	3,098	3,722
Estimate of Fair Value Measurement [Member] \| Due within one year [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable:	7,363,251	8,079,309
Estimate of Fair Value Measurement [Member] \| Long-term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable:	$ 8,348,709	$ 7,445,545

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Variable Interest Entity, Consolidated, Fair Value Disclosure, Liabilities

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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The carrying amount of the contractual right to receive fees, as compensation in exchange for providing a guarantee to a third party, over life of the guarantee.

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Fair value portion of notes payable.

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