Loans and Allowance for Losses and Concentrations of Credit Risk - Financing Receivables Credit Quality Indicators (Details) - USD ($) $ in Thousands		Sep. 30, 2017		Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[2],[3]	$ 6,557,030		$ 6,139,304
Financing Receivable, Recorded Investment, Past Due	[4]	66,381	[1]	21,038	[5]
Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	6,147,368		5,845,308
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	190,020		128,803
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	219,642		165,193
Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	3,593,716		3,410,498
Financing Receivable, Recorded Investment, Past Due		32,275	[1]	13,822	[5]
Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	3,373,204		3,281,371
Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	116,318		55,645
Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	104,194		73,482
Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	1,184,221		1,037,440
Financing Receivable, Recorded Investment, Past Due		22,330	[1]	3,652	[5]
Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	1,097,031		971,477
Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	15,383		18,020
Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	71,807		47,943
Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	1,309,743		1,305,844
Financing Receivable, Recorded Investment, Past Due		7,367	[1]	707	[5]
Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	1,230,873		1,228,840
Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	51,110		48,416
Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	27,760		28,588
Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	407,708		324,074
Financing Receivable, Recorded Investment, Past Due		3,766	[1]	2,857	[5]
Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	389,293		304,728
Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	7,040		6,716
Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	11,375		12,630
Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	48,068		48,051
Financing Receivable, Recorded Investment, Past Due		0	[1]	0	[5]
Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	44,750		46,082
Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	0		0
Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	3,318		1,969
Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	13,574		13,397
Financing Receivable, Recorded Investment, Past Due		643	[1]	0	[5]
Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	12,217		12,810
Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	169		6
Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	1,188		581
On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	4,068,893		3,514,454
Financing Receivable, Recorded Investment, Past Due	[4]	65,105	[1]	19,757	[5]
On-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	3,867,418		3,352,959
On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	70,725		73,809
On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	130,750		87,686
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	2,347,023		2,157,098
Financing Receivable, Recorded Investment, Past Due		31,413	[1]	13,449	[5]
On-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	2,240,054		2,080,227
On-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	38,647		35,223
On-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	68,322		41,648
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	808,476		597,130
Financing Receivable, Recorded Investment, Past Due		22,330	[1]	3,245	[5]
On-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	760,251		568,221
On-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	7,024		1,139
On-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	41,201		27,770
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	637,015		548,517
Financing Receivable, Recorded Investment, Past Due		7,367	[1]	669	[5]
On-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	603,653		504,784
On-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	19,846		33,075
On-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	13,516		10,658
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	253,485		191,270
Financing Receivable, Recorded Investment, Past Due		3,352	[1]	2,394	[5]
On-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	241,208		179,288
On-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	5,208		4,372
On-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	7,069		7,610
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	13,248		11,545
Financing Receivable, Recorded Investment, Past Due		0	[1]	0	[5]
On-balance sheet [Member] | Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	13,248		11,545
On-balance sheet [Member] | Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	0		0
On-balance sheet [Member] | Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	0		0
On-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	9,646		8,894
Financing Receivable, Recorded Investment, Past Due		643	[1]	0	[5]
On-balance sheet [Member] | Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	9,004		8,894
On-balance sheet [Member] | Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	0		0
On-balance sheet [Member] | Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	642		0
Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	2,488,137		2,624,850
Financing Receivable, Recorded Investment, Past Due	[4]	1,276	[1]	1,281	[5]
Off-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	2,279,950		2,492,349
Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	119,295		54,994
Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	88,892		77,507
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	1,246,693		1,253,400
Financing Receivable, Recorded Investment, Past Due		862	[1]	373	[5]
Off-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	1,133,150		1,201,144
Off-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	77,671		20,422
Off-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	35,872		31,834
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	375,745		440,310
Financing Receivable, Recorded Investment, Past Due		0	[1]	407	[5]
Off-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	336,780		403,256
Off-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	8,359		16,881
Off-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	30,606		20,173
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	672,728		757,327
Financing Receivable, Recorded Investment, Past Due		0	[1]	38	[5]
Off-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	627,220		724,056
Off-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	31,264		15,341
Off-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	14,244		17,930
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	154,223		132,804
Financing Receivable, Recorded Investment, Past Due		414	[1]	463	[5]
Off-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	148,085		125,440
Off-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	1,832		2,344
Off-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	4,306		5,020
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	34,820		36,506
Financing Receivable, Recorded Investment, Past Due		0	[1]	0	[5]
Off-balance sheet [Member] | Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	31,502		34,537
Off-balance sheet [Member] | Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	0		0
Off-balance sheet [Member] | Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	3,318		1,969
Off-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	3,928		4,503
Financing Receivable, Recorded Investment, Past Due		0	[1]	0	[5]
Off-balance sheet [Member] | Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1]	3,213		3,916
Off-balance sheet [Member] | Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[6]	169		6
Off-balance sheet [Member] | Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Gross	[1],[7]	$ 546		$ 581

[1] Amounts represent unpaid principal balance of risk-rated loans, which is the basis Farmer Mac uses to analyze its portfolio, and recorded investment of past due loans.

[2] As of second quarter 2017, Farmer Mac revised its calculation of the original loan-to-value ratio of a loan to combine for any cross-collateralized loans: (i) the original loan principal balance amounts in the numerator and (ii) the original appraised property values in the denominator. In previous periods, the ratio was calculated on a loan-by-loan basis without considering the effects of any cross-collateralization. Prior period information has been reclassified to conform to the current period calculation and presentation.

[3] Geographic regions: Northwest (AK, ID, MT, OR, WA, WY); Southwest (AZ, CA, CO, HI, NM, NV, UT); Mid-North (IA, IL, IN, MI, MN, NE, ND, SD, WI); Mid-South (AR, KS, LA, MO, OK, TX); Northeast (CT, DE, KY, MA, MD, ME, NH, NJ, NY, OH, PA, RI, VA, VT, WV); Southeast (AL, FL, GA, MS, NC, SC, TN).

[4] Includes loans and loans underlying off-balance sheet Farm & Ranch Guaranteed Securities and LTSPCs that are 90 days or more past due, in foreclosure, or in bankruptcy with at least one missed payment, excluding loans performing under either their original loan terms or a court-approved bankruptcy plan.

[5] Amounts represent unpaid principal balance of risk-rated loans, which is the basis Farmer Mac uses to analyze its portfolio, and recorded investment of past due loans.

[6] Assets in the "Special mention" category generally have potential weaknesses due to performance issues but are currently considered to be adequately secured.

[7] Substandard assets have a well-defined weakness or weaknesses and there is a distinct possibility that some loss will be sustained if deficiencies are not corrected.