Business Segment Reporting - Core Earnings - Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016		Dec. 31, 2016
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	$ 39,731		$ 34,358		$ 76,802		$ 67,998
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	3,472	[3]	3,655	[6]	7,316	[9]	7,281	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	272	[2],[13]	(3,889)	[5],[14]	3,224	[8],[15]	(10,221)	[11],[16]
Non-interest income/(loss)	3,744		(234)		10,540		(2,940)
Provision for loan losses	(327)		(364)		(964)		(413)
Provision for Other Credit Losses	139		94		(54)		108
Noninterest Expense, Excluding Loan, Lease and Other Losses	(11,251)		(9,980)		(21,993)		(19,932)
Non-interest expense	11,390	[17]	10,074	[18]	21,939	[19]	20,040	[20]
Income Tax Expense (Benefit)	11,124		8,400		21,910		15,735
Net income	20,634		15,286		42,529		28,870
Net income	31,758		23,686		64,439		44,605
Preferred Stock Dividends, Income Statement Impact	(3,296)		(3,296)		(6,591)		(6,591)
Less: Net loss attributable to non-controlling interest	150		16		165		44
Net Income (Loss) Available to Common Stockholders, Basic	17,488		12,006		36,103		22,323
Segment Reporting Information, Additional Information [Abstract]
Total Assets	17,267,385		16,823,190		17,267,385		16,823,190		$ 15,606,020
On and Off Balance Sheet Program Assets, At Principal Balance	18,258,858		17,116,536		18,258,858		17,116,536
Farm & Ranch [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	13,338		11,606		26,092		22,733
Less: reconciling adjustments(1)(2)(3)	(2,007)	[1],[2],[3]	(1,731)	[4],[5],[6]	(4,077)	[7],[8],[9]	(3,397)	[10],[11],[12]
Net Effective Spread	11,331		9,875		22,015		19,336
Guaranty Fee Income	4,191	[3]	3,965	[6]	8,486	[9]	7,874	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	994	[2],[13]	78	[5],[14]	1,188	[8],[15]	175	[11],[16]
Non-interest income/(loss)	5,185		4,043		9,674		8,049
Provision for loan losses	(327)		(364)		(964)		(413)
Provision for Other Credit Losses	139		94		(54)		108
Noninterest Expense, Excluding Loan, Lease and Other Losses	(4,446)		(4,112)		(8,511)		(8,273)
Non-interest expense	4,585	[17]	4,206	[18]	8,457	[19]	8,381	[20]
Segment core earnings before income taxes	11,604		9,348		22,268		18,591
Income Tax Expense (Benefit)	4,061		3,272		7,793		6,508
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	7,543		6,076		14,475		12,083
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest	0		0		0		0
Segment core earnings	7,543		6,076		14,475		12,083
Segment Reporting Information, Additional Information [Abstract]
Total Assets	3,958,344		3,311,270		3,958,344		3,311,270
On and Off Balance Sheet Program Assets, At Principal Balance	6,426,518		5,830,533		6,426,518		5,830,533
USDA Guarantees [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	5,176		4,938		10,459		9,990
Less: reconciling adjustments(1)(2)(3)	(495)	[1],[2],[3]	(350)	[4],[5],[6]	(1,075)	[7],[8],[9]	(1,094)	[10],[11],[12]
Net Effective Spread	4,681		4,588		9,384		8,896
Guaranty Fee Income	99	[3]	14	[6]	173	[9]	21	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	11	[2],[13]	25	[5],[14]	25	[8],[15]	83	[11],[16]
Non-interest income/(loss)	110		39		198		104
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	(1,166)		(1,092)		(2,253)		(2,185)
Non-interest expense	1,166	[17]	1,092	[18]	2,253	[19]	2,185	[20]
Segment core earnings before income taxes	3,625		3,535		7,329		6,815
Income Tax Expense (Benefit)	1,269		1,237		2,565		2,385
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	2,356		2,298		4,764		4,430
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest	0		0		0		0
Segment core earnings	2,356		2,298		4,764		4,430
Segment Reporting Information, Additional Information [Abstract]
Total Assets	2,141,569		2,046,516		2,141,569		2,046,516
On and Off Balance Sheet Program Assets, At Principal Balance	2,237,013		1,960,358		2,237,013		1,960,358
Rural Utilities [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	3,003		2,855		5,951		5,719
Less: reconciling adjustments(1)(2)(3)	(267)	[1],[2],[3]	(293)	[4],[5],[6]	(576)	[7],[8],[9]	(619)	[10],[11],[12]
Net Effective Spread	2,736		2,562		5,375		5,100
Guaranty Fee Income	487	[3]	373	[6]	979	[9]	668	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	5	[2],[13]	0	[5],[14]	10	[8],[15]	0	[11],[16]
Non-interest income/(loss)	492		373		989		668
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	(643)		(830)		(1,230)		(1,661)
Non-interest expense	643	[17]	830	[18]	1,230	[19]	1,661	[20]
Segment core earnings before income taxes	2,585		2,105		5,134		4,107
Income Tax Expense (Benefit)	905		737		1,797		1,438
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	1,680		1,368		3,337		2,669
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest	0		0		0		0
Segment core earnings	1,680		1,368		3,337		2,669
Segment Reporting Information, Additional Information [Abstract]
Total Assets	1,038,383		1,023,630		1,038,383		1,023,630
On and Off Balance Sheet Program Assets, At Principal Balance	1,883,909		1,934,473		1,883,909		1,934,473
Institutional Credit [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	15,431		12,109		28,933		23,858
Less: reconciling adjustments(1)(2)(3)	(1,036)	[1],[2],[3]	(702)	[4],[5],[6]	(1,957)	[7],[8],[9]	(1,361)	[10],[11],[12]
Net Effective Spread	14,395		11,407		26,976		22,497
Guaranty Fee Income	165	[3]	458	[6]	620	[9]	916	[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/(loss)	165		458		620		916
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	(1,622)		(538)		(3,143)		(1,077)
Non-interest expense	1,622	[17]	538	[18]	3,143	[19]	1,077	[20]
Segment core earnings before income taxes	12,938		11,327		24,453		22,336
Income Tax Expense (Benefit)	4,528		3,964		8,558		7,816
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	8,410		7,363		15,895		14,520
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest	0		0		0		0
Segment core earnings	8,410		7,363		15,895		14,520
Segment Reporting Information, Additional Information [Abstract]
Total Assets	7,425,774		6,071,924		7,425,774		6,071,924
On and Off Balance Sheet Program Assets, At Principal Balance	7,711,418		7,391,172		7,711,418		7,391,172
Corporate Segment [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	2,783		2,850		5,367		5,698
Less: reconciling adjustments(1)(2)(3)	(316)	[1],[2],[3]	(256)	[4],[5],[6]	(641)	[7],[8],[9]	(552)	[10],[11],[12]
Net Effective Spread	2,467		2,594		4,726		5,146
Guaranty Fee Income	0	[3]	0	[6]	0	[9]	0	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	(450)	[2],[13]	(228)	[5],[14]	393	[8],[15]	(900)	[11],[16]
Non-interest income/(loss)	(450)		(228)		393		(900)
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	(3,374)		(3,408)		(6,856)		(6,736)
Non-interest expense	3,374	[17]	3,408	[18]	6,856	[19]	6,736	[20]
Segment core earnings before income taxes	(1,357)		(1,042)		(1,737)		(2,490)
Income Tax Expense (Benefit)	(466)		(254)		(1,251)		(747)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	(891)		(788)		(486)		(1,743)
Preferred Stock Dividends, Income Statement Impact	(3,296)		(3,296)		(6,591)		(6,591)
Less: Net loss attributable to non-controlling interest	150		16		165		44
Segment core earnings	(4,037)		(4,068)		(6,912)		(8,290)
Segment Reporting Information, Additional Information [Abstract]
Total Assets	2,703,315		4,369,850		2,703,315		4,369,850
Segment Reconciling Items [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	0		0		0		0
Less: reconciling adjustments(1)(2)(3)	4,121	[1],[2],[3]	3,332	[4],[5],[6]	8,326	[7],[8],[9]	7,023	[10],[11],[12]
Net Effective Spread	4,121		3,332		8,326		7,023
Guaranty Fee Income	(1,470)	[3]	(1,155)	[6]	(2,942)	[9]	(2,198)	[12]
Other Non-Interest Income (Expense), Excluding Guarantee and Commitment Fees	(288)	[2],[13]	(3,764)	[5],[14]	1,608	[8],[15]	(9,579)	[11],[16]
Non-interest income/(loss)	(1,758)		(4,919)		(1,334)		(11,777)
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	2,363	[21]	(1,587)	[22]	6,992	[21]	(4,754)	[22]
Income Tax Expense (Benefit)	827		(556)		2,448		(1,665)
Segment core earnings before preferred stock dividends and attibution of income to non-controlling interest - preferred stock dividends	1,536	[21]	(1,031)	[22]	4,544	[21]	(3,089)	[22]
Preferred Stock Dividends, Income Statement Impact	0		0		0		0
Less: Net loss attributable to non-controlling interest	0		0		0		0
Segment core earnings	1,536	[21]	(1,031)	[22]	4,544	[21]	(3,089)	[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 "(Losses)/gains 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 "(Losses)/gains 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 "(Losses)/gains 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 "(Losses)/gains 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. The exchange of variation margin, whether considered a partial settlement of or the pledge of collateral under a derivatives contract, 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. The exchange of variation margin, whether considered a partial settlement of or the pledge of collateral under a derivatives contract, 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.