Loans and Allowance for Losses and Concentrations of Credit Risk - Allowance for Losses by Impairment Method and Commodity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Mar. 31, 2014	Dec. 31, 2013		Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	$ 5,222,701			$ 5,068,039
Financing Receivable, Individually Evaluated for Impairment	87,963			95,041
Financing Receivable, Gross	5,310,664	[1]		5,163,080	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	8,792			10,638
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	2,573			2,696
Total Allowance for Losses	11,365		13,979	13,334		13,478	14,252	16,890
Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	2,811,557			2,643,748
Financing Receivable, Individually Evaluated for Impairment	21,228			23,109
Financing Receivable, Gross	2,832,785	[1]		2,666,857	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	2,034			1,718
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	356			406
Total Allowance for Losses	2,390		2,278	2,124		2,405	2,617	2,589
Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	864,689			862,969
Financing Receivable, Individually Evaluated for Impairment	42,113			44,855
Financing Receivable, Gross	906,802	[1]		907,824	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	531			484
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	1,686			1,702
Total Allowance for Losses	2,217		2,131	2,186		2,168	2,326	2,316
Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	1,244,426			1,232,062
Financing Receivable, Individually Evaluated for Impairment	12,403			14,043
Financing Receivable, Gross	1,256,829	[1]		1,246,105	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,144			1,078
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	167			193
Total Allowance for Losses	1,311		1,387	1,271		1,279	1,587	1,534
Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	146,007			149,824
Financing Receivable, Individually Evaluated for Impairment	12,219			12,919
Financing Receivable, Gross	158,226	[1]		162,743	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	80			62
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	364			392
Total Allowance for Losses	444		464	454		425	733	784
Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	147,840			170,918
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	147,840	[1]		170,918	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,999			7,292
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Total Allowance for Losses	4,999		7,715	7,292		7,196	6,971	9,661
Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	8,182			8,518
Financing Receivable, Individually Evaluated for Impairment	0			115
Financing Receivable, Gross	8,182	[1]		8,633	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4			4
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			3
Total Allowance for Losses	4		4	7		5	18	6
On-balance sheet [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	2,251,963			2,051,498
Financing Receivable, Individually Evaluated for Impairment	75,204			83,969
Financing Receivable, Gross	2,327,167	[1]		2,135,467	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	3,495			4,392
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	2,275			2,474
Total Allowance for Losses	5,770			6,866
On-balance sheet [Member] | Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	1,487,792			1,363,861
Financing Receivable, Individually Evaluated for Impairment	18,011			21,147
Financing Receivable, Gross	1,505,803	[1]		1,385,008	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	1,723			1,321
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	269			362
Total Allowance for Losses	1,992			1,683
On-balance sheet [Member] | Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	318,616			295,037
Financing Receivable, Individually Evaluated for Impairment	38,782			41,441
Financing Receivable, Gross	357,398	[1]		336,478	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	369			325
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	1,594			1,641
Total Allowance for Losses	1,963			1,966
On-balance sheet [Member] | Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	368,556			319,665
Financing Receivable, Individually Evaluated for Impairment	8,094			10,844
Financing Receivable, Gross	376,650	[1]		330,509	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	615			436
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	103			140
Total Allowance for Losses	718			576
On-balance sheet [Member] | Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	40,744			39,940
Financing Receivable, Individually Evaluated for Impairment	10,317			10,422
Financing Receivable, Gross	51,061	[1]		50,362	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	32			20
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	309			331
Total Allowance for Losses	341			351
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	35,593			32,636
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	35,593	[1]		32,636	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	756			2,290
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Total Allowance for Losses	756			2,290
On-balance sheet [Member] | Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	662			359
Financing Receivable, Individually Evaluated for Impairment	0			115
Financing Receivable, Gross	662	[1]		474	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	0			0
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Total Allowance for Losses	0			0
Off-balance sheet [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	2,970,738			3,016,541
Financing Receivable, Individually Evaluated for Impairment	12,759			11,072
Financing Receivable, Gross	2,983,497	[1]		3,027,613	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	5,297			6,246
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	298			222
Total Allowance for Losses	5,595			6,468
Off-balance sheet [Member] | Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	1,323,765			1,279,887
Financing Receivable, Individually Evaluated for Impairment	3,217			1,962
Financing Receivable, Gross	1,326,982	[1]		1,281,849	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	311			397
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	87			44
Total Allowance for Losses	398			441
Off-balance sheet [Member] | Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	546,073			567,932
Financing Receivable, Individually Evaluated for Impairment	3,331			3,414
Financing Receivable, Gross	549,404	[1]		571,346	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	162			159
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	92			61
Total Allowance for Losses	254			220
Off-balance sheet [Member] | Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	875,870			912,397
Financing Receivable, Individually Evaluated for Impairment	4,309			3,199
Financing Receivable, Gross	880,179	[1]		915,596	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	529			642
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	64			53
Total Allowance for Losses	593			695
Off-balance sheet [Member] | Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	105,263			109,884
Financing Receivable, Individually Evaluated for Impairment	1,902			2,497
Financing Receivable, Gross	107,165	[1]		112,381	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	48			42
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	55			61
Total Allowance for Losses	103			103
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	112,247			138,282
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	112,247	[1]		138,282	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,243			5,002
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			0
Total Allowance for Losses	4,243			5,002
Off-balance sheet [Member] | Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Collectively Evaluated for Impairment	7,520			8,159
Financing Receivable, Individually Evaluated for Impairment	0			0
Financing Receivable, Gross	7,520	[1]		8,159	[1]
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4			4
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0			3
Total Allowance for Losses	$ 4			$ 7

[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.