Business Segment Reporting - Core Earnings - Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016		Dec. 31, 2016
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	$ 39,562		$ 35,563		$ 116,364		$ 103,561
Less: reconciling adjustments(1)(2)(3)	0	[1],[2],[3]	0	[4],[5],[6]	0	[7],[8],[9]	0	[10],[11],[12]
Net Effective Spread	0		0		0		0
Guaranty Fee Income	3,314	[3]	3,798	[6]	10,630	[9]	11,079	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	985	[2],[13]	303	[5],[14]	4,209	[8],[15]	(9,918)	[11],[16]
Non-interest income	4,299		4,101		14,839		1,161
Provision for loan losses	(270)		(191)		(1,234)		(604)
Provision for Other Credit Losses	114		(222)		60		(114)
Noninterest Expense, Excluding Loan, Lease and Other Losses	(10,502)		(9,525)		(32,495)		(29,457)
Non-interest expense	10,616	[17]	9,303	[18]	32,555	[19]	29,343	[20]
Income Tax Expense (Benefit)	11,193		10,529		33,103		26,264
Net income	21,782		19,641		64,311		48,511
Net income	32,975		30,170		97,414		74,775
Preferred Stock Dividends, Income Statement Impact	(3,295)		(3,295)		(9,886)		(9,886)
Less: Net loss attributable to non-controlling interest	0		18		165		62
Net Income (Loss) Available to Common Stockholders, Basic	18,487		16,364		54,590		38,687
Segment Reporting Information, Additional Information [Abstract]
Total Assets	17,690,238		16,000,905		17,690,238		16,000,905		$ 15,606,020
On and Off Balance Sheet Program Assets, At Principal Balance	18,644,273		17,247,739		18,644,273		17,247,739
Farm & Ranch [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	13,609		12,039		39,701		34,772
Less: reconciling adjustments(1)(2)(3)	(2,131)	[1],[2],[3]	(1,336)	[4],[5],[6]	(6,208)	[7],[8],[9]	(4,733)	[10],[11],[12]
Net Effective Spread	11,478		10,703		33,493		30,039
Guaranty Fee Income	4,236	[3]	3,516	[6]	12,722	[9]	11,390	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	214	[2],[13]	276	[5],[14]	1,402	[8],[15]	451	[11],[16]
Non-interest income	4,450		3,792		14,124		11,841
Provision for loan losses	(270)		(191)		(1,234)		(604)
Provision for Other Credit Losses	114		(222)		60		(114)
Noninterest Expense, Excluding Loan, Lease and Other Losses	(4,077)		(3,673)		(12,588)		(11,946)
Non-interest expense	4,191	[17]	3,451	[18]	12,648	[19]	11,832	[20]
Segment core earnings before income taxes	11,467		10,853		33,735		29,444
Income Tax Expense (Benefit)	4,014		3,799		11,806		10,307
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	7,453		7,054		21,929		19,137
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest			0		0		0
Segment core earnings	7,453		7,054		21,929		19,137
Segment Reporting Information, Additional Information [Abstract]
Total Assets	4,128,778		3,436,641		4,128,778		3,436,641
On and Off Balance Sheet Program Assets, At Principal Balance	6,557,030		6,004,728		6,557,030		6,004,728
USDA Guarantees [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	5,288		5,753		15,747		15,743
Less: reconciling adjustments(1)(2)(3)	(433)	[1],[2],[3]	(564)	[4],[5],[6]	(1,508)	[7],[8],[9]	(1,658)	[10],[11],[12]
Net Effective Spread	4,855		5,189		14,239		14,085
Guaranty Fee Income	130	[3]	29	[6]	303	[9]	50	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	9	[2],[13]	95	[5],[14]	34	[8],[15]	178	[11],[16]
Non-interest income	139		124		337		228
Provision for loan losses	0		0		0		0
Provision for Other Credit Losses			0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(1,080)		(933)		(3,333)		(3,118)
Non-interest expense	1,080	[17]	933	[18]	3,333	[19]	3,118	[20]
Segment core earnings before income taxes	3,914		4,380		11,243		11,195
Income Tax Expense (Benefit)	1,370		1,533		3,935		3,918
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	2,544		2,847		7,308		7,277
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest			0		0		0
Segment core earnings	2,544		2,847		7,308		7,277
Segment Reporting Information, Additional Information [Abstract]
Total Assets	2,165,749		2,062,195		2,165,749		2,062,195
On and Off Balance Sheet Program Assets, At Principal Balance	2,298,956		2,020,834		2,298,956		2,020,834
Rural Utilities [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	2,230		2,963		8,181		8,682
Less: reconciling adjustments(1)(2)(3)	602	[1],[2],[3]	(320)	[4],[5],[6]	26	[7],[8],[9]	(939)	[10],[11],[12]
Net Effective Spread	2,832		2,643		8,207		7,743
Guaranty Fee Income	476	[3]	529	[6]	1,455	[9]	1,197	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	5	[2],[13]	0	[5],[14]	15	[8],[15]	0	[11],[16]
Non-interest income	481		529		1,470		1,197
Provision for loan losses	0		0		0		0
Provision for Other Credit Losses			0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(608)		(553)		(1,838)		(2,214)
Non-interest expense	608	[17]	553	[18]	1,838	[19]	2,214	[20]
Segment core earnings before income taxes	2,705		2,619		7,839		6,726
Income Tax Expense (Benefit)	947		917		2,744		2,355
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	1,758		1,702		5,095		4,371
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest			0		0		0
Segment core earnings	1,758		1,702		5,095		4,371
Segment Reporting Information, Additional Information [Abstract]
Total Assets	1,073,525		1,008,903		1,073,525		1,008,903
On and Off Balance Sheet Program Assets, At Principal Balance	1,886,445		1,867,666		1,886,445		1,867,666
Institutional Credit [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	15,431		12,226		44,364		36,084
Less: reconciling adjustments(1)(2)(3)	(1,068)	[1],[2],[3]	(799)	[4],[5],[6]	(3,025)	[7],[8],[9]	(2,160)	[10],[11],[12]
Net Effective Spread	14,363		11,427		41,339		33,924
Guaranty Fee Income	93	[3]	459	[6]	713	[9]	1,375	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	0	[2],[13]	0	[5],[14]	0	[8],[15]	0	[11],[16]
Non-interest income	93		459		713		1,375
Provision for loan losses	0		0		0		0
Provision for Other Credit Losses			0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(1,670)		(1,253)		(4,813)		(2,330)
Non-interest expense	1,670	[17]	1,253	[18]	4,813	[19]	2,330	[20]
Segment core earnings before income taxes	12,786		10,633		37,239		32,969
Income Tax Expense (Benefit)	4,475		3,722		13,033		11,538
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	8,311		6,911		24,206		21,431
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest			0		0		0
Segment core earnings	8,311		6,911		24,206		21,431
Segment Reporting Information, Additional Information [Abstract]
Total Assets	7,612,572		6,045,227		7,612,572		6,045,227
On and Off Balance Sheet Program Assets, At Principal Balance	7,901,842		7,354,511		7,901,842		7,354,511
Corporate Segment [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	3,004		2,582		8,371		8,280
Less: reconciling adjustments(1)(2)(3)	(305)	[1],[2],[3]	(345)	[4],[5],[6]	(946)	[7],[8],[9]	(897)	[10],[11],[12]
Net Effective Spread	2,699		2,237		7,425		7,383
Guaranty Fee Income		[3]	0	[6]	0	[9]	0	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	233	[2],[13]	(388)	[5],[14]	626	[8],[15]	(1,288)	[11],[16]
Non-interest income	233		(388)		626		(1,288)
Provision for loan losses	0		0		0		0
Provision for Other Credit Losses			0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	(3,067)		(3,113)		(9,923)		(9,849)
Non-interest expense	3,067	[17]	3,113	[18]	9,923	[19]	9,849	[20]
Segment core earnings before income taxes	(135)		(1,264)		(1,872)		(3,754)
Income Tax Expense (Benefit)	(396)		(474)		(1,646)		(1,221)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	261		(790)		(226)		(2,533)
Preferred Stock Dividends, Income Statement Impact	(3,295)		(3,295)		(9,886)		(9,886)
Less: Net loss attributable to non-controlling interest			18		165		62
Segment core earnings	(3,034)		(4,067)		(9,947)		(12,357)
Segment Reporting Information, Additional Information [Abstract]
Total Assets	2,709,614		3,447,939		2,709,614		3,447,939
Segment Reconciling Items [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	0		0		0		0
Less: reconciling adjustments(1)(2)(3)	3,335	[1],[2],[3]	3,364	[4],[5],[6]	11,661	[7],[8],[9]	10,387	[10],[11],[12]
Net Effective Spread	3,335		3,364		11,661		10,387
Guaranty Fee Income	(1,621)	[3]	(735)	[6]	(4,563)	[9]	(2,933)	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	524	[2],[13]	320	[5],[14]	2,132	[8],[15]	(9,259)	[11],[16]
Non-interest income	(1,097)		(415)		(2,431)		(12,192)
Provision for loan losses	0		0		0		0
Provision for Other Credit Losses	0		0		0		0
Noninterest Expense, Excluding Loan, Lease and Other Losses	0		0		0		0
Non-interest expense	0	[17]	0	[18]	0	[19]	0	[20]
Segment core earnings before income taxes	2,238	[21]	2,949	[22]	9,230	[21]	(1,805)	[22]
Income Tax Expense (Benefit)	783		1,032		3,231		(633)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	1,455	[21]	1,917	[22]	5,999	[21]	(1,172)	[22]
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest			0		0		0
Segment core earnings	1,455	[21]	1,917	[22]	5,999	[21]	(1,172)	[22]
Segment Reporting Information, Additional Information [Abstract]
Total Assets	0		0		0		0
On and Off Balance Sheet Program Assets, At Principal Balance	$ 0		$ 0		$ 0		$ 0

[1] Excludes the amortization of premiums and discounts on assets consolidated at fair value, originally included in interest income, to reflect core earnings amounts.

[2] Includes the reclassification of interest expense related to interest rate swaps not designated as hedges, which are included in "Gains/(losses) on financial derivatives and hedging activities" on the consolidated financial statements, to determine the effective funding cost for each operating segment.

[3] Includes the reclassification of interest income and interest expense from consolidated trusts owned by third parties to guarantee and commitment fees, to reflect management's view that the net interest income Farmer Mac earns is effectively a guarantee fee.

[4] Excludes the amortization of premiums and discounts on assets consolidated at fair value, originally included in interest income, to reflect core earnings amounts.

[5] Includes the reclassification of interest expense related to interest rate swaps not designated as hedges, which are included in "Gains/(losses) on financial derivatives and hedging activities" on the consolidated financial statements, to determine the effective funding cost for each operating segment.

[6] Includes the reclassification of interest income and interest expense from consolidated trusts owned by third parties to guarantee and commitment fees, to reflect management's view that the net interest income Farmer Mac earns is effectively a guarantee fee.

[7] Excludes the amortization of premiums and discounts on assets consolidated at fair value, originally included in interest income, to reflect core earnings amounts.

[8] Includes the reclassification of interest expense related to interest rate swaps not designated as hedges, which are included in "Gains/(losses) on financial derivatives and hedging activities" on the consolidated financial statements, to determine the effective funding cost for each operating segment.

[9] Includes the reclassification of interest income and interest expense from consolidated trusts owned by third parties to guarantee and commitment fees, to reflect management's view that the net interest income Farmer Mac earns is effectively a guarantee fee.

[10] Excludes the amortization of premiums and discounts on assets consolidated at fair value, originally included in interest income, to reflect core earnings amounts.

[11] Includes the reclassification of interest expense related to interest rate swaps not designated as hedges, which are included in "Gains/(losses) on financial derivatives and hedging activities" on the consolidated financial statements, to determine the effective funding cost for each operating segment.

[12] Includes the reclassification of interest income and interest expense from consolidated trusts owned by third parties to guarantee and commitment fees, to reflect management's view that the net interest income Farmer Mac earns is effectively a guarantee fee.

[13] Includes reconciling adjustments for fair value adjustments on financial derivatives and trading assets. Also includes a reconciling adjustment related to the recognition of deferred gains over the estimated lives of certain Farmer Mac Guaranteed Securities and USDA Securities. In 2016 and prior periods, fair value adjustments on financial derivatives included variation margin payment amounts because those amounts were considered to be collateral of the related exposure and were accounted for as unrealized gains or losses. However, effective first quarter 2017, CME implemented a change in its rules related to the exchange of variation margin, whereby variation margin payments are considered to be a partial settlement of the respective derivatives contracts rather than as pledged collateral, and accounted for as realized gains and losses. See Note 4 for more information about this rule change. Farmer Mac believes that even though these variation margin amounts are now accounted for as realized gains or losses on financial derivatives and hedging activities as a result of the CME rule change, their economic character will remain the same as they were before the change. This is not expected to have a cumulative net impact on Farmer Mac's financial condition or results of operations reported in accordance with GAAP because the related financial instruments are expected to be held to maturity. Therefore, beginning in 2017, this reconciling adjustment includes realized gains and losses on financial derivatives centrally cleared through CME resulting from the exchange of variation margin. As a result, core earnings subsequent to 2016 will be presented on a consistent basis with core earnings in 2016 and prior periods.

[14] Includes reconciling adjustments for fair value adjustments on financial derivatives and trading assets. Also includes a reconciling adjustment related to the recognition of deferred gains over the estimated lives of certain Farmer Mac Guaranteed Securities and USDA Securities.

[15] Includes reconciling adjustments for fair value adjustments on financial derivatives and trading assets. Also includes a reconciling adjustment related to the recognition of deferred gains over the estimated lives of certain Farmer Mac Guaranteed Securities and USDA Securities. In 2016 and prior periods, fair value adjustments on financial derivatives included variation margin payment amounts because those amounts were considered to be collateral of the related exposure and were accounted for as unrealized gains or losses. However, effective first quarter 2017, CME implemented a change in its rules related to the exchange of variation margin, whereby variation margin payments are considered to be a partial settlement of the respective derivatives contracts rather than as pledged collateral, and accounted for as realized gains and losses. See Note 4 for more information about this rule change. Farmer Mac believes that even though these variation margin amounts are now accounted for as realized gains or losses on financial derivatives and hedging activities as a result of the CME rule change, their economic character will remain the same as they were before the change. This is not expected to have a cumulative net impact on Farmer Mac's financial condition or results of operations reported in accordance with GAAP because the related financial instruments are expected to be held to maturity. Therefore, beginning in 2017, this reconciling adjustment includes realized gains and losses on financial derivatives centrally cleared through CME resulting from the exchange of variation margin. As a result, core earnings subsequent to 2016 will be presented on a consistent basis with core earnings in 2016 and prior periods.

[16] Includes reconciling adjustments for fair value adjustments on financial derivatives and trading assets. Also includes a reconciling adjustment related to the recognition of deferred gains over the estimated lives of certain Farmer Mac Guaranteed Securities and USDA Securities.

[17] Includes directly attributable costs and an allocation of indirectly attributable costs based on staffing.

[18] Includes directly attributable costs and an allocation of indirectly attributable costs based on staffing.

[19] Includes directly attributable costs and an allocation of indirectly attributable costs based on staffing.

[20] Includes directly attributable costs and an allocation of indirectly attributable costs based on staffing.

[21] Net adjustments to reconcile to the corresponding income measures: core earnings before income taxes reconciled to income before income taxes; core earnings before preferred stock dividends and attribution of income to non-controlling interest reconciled to net income; and segment core earnings reconciled to net income attributable to common stockholders.

[22] Net adjustments to reconcile to the corresponding income measures: core earnings before income taxes reconciled to income before income taxes; core earnings before preferred stock dividends and attribution of income to non-controlling interest reconciled to net income; and segment core earnings reconciled to net income attributable to common stockholders.