Loans and Allowance for Losses and Concentrations of Credit Risk Impaired Financing Receivables (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 100,699		$ 90,410
Impaired Financing Receivable, Recorded Investment	100,351		88,363
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	30,638		24,295
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	30,236		25,691
Impaired Financing Receivable, with Related Allowance, Recorded Investment	69,713		64,068
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	68,601		62,335
Impaired Financing Receivable, Unpaid Principal Balance	98,837		88,026
Impaired Financing Receivable, Related Allowance	6,659		7,296
Financing Receivable, Recorded Investment, Nonaccrual Status	45,335	[1]	45,338	[1]
Impaired Financing Receivable, Interest Income, Accrual Method	2,694		2,546
Crops [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	28,568		30,400
Impaired Financing Receivable, Recorded Investment	24,509		29,818
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	7,295		6,809
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	7,247		7,446
Impaired Financing Receivable, with Related Allowance, Recorded Investment	17,214		23,009
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	16,829		22,074
Impaired Financing Receivable, Unpaid Principal Balance	24,076		29,520
Impaired Financing Receivable, Related Allowance	706		2,410
Financing Receivable, Recorded Investment, Nonaccrual Status	11,888	[1]	9,214	[1]
Impaired Financing Receivable, Interest Income, Accrual Method	293		549
Permanent Plantings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	35,071		29,806
Impaired Financing Receivable, Recorded Investment	38,219		28,751
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	11,652		10,083
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	11,509		9,957
Impaired Financing Receivable, with Related Allowance, Recorded Investment	26,567		18,668
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	26,095		18,288
Impaired Financing Receivable, Unpaid Principal Balance	37,604		28,245
Impaired Financing Receivable, Related Allowance	1,515		2,324
Financing Receivable, Recorded Investment, Nonaccrual Status	15,789	[1]	25,710	[1]
Impaired Financing Receivable, Interest Income, Accrual Method	1,823		1,009
Livestock [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	15,379		12,732
Impaired Financing Receivable, Recorded Investment	17,004		10,284
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	7,644		3,248
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	7,489		4,088
Impaired Financing Receivable, with Related Allowance, Recorded Investment	9,360		7,036
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	9,219		6,796
Impaired Financing Receivable, Unpaid Principal Balance	16,708		10,884
Impaired Financing Receivable, Related Allowance	355		407
Financing Receivable, Recorded Investment, Nonaccrual Status	5,141	[1]	3,483	[1]
Impaired Financing Receivable, Interest Income, Accrual Method	263		426
Part-Time Farm [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	15,953		10,329
Impaired Financing Receivable, Recorded Investment	15,258		12,633
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,140		3,241
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,090		3,298
Impaired Financing Receivable, with Related Allowance, Recorded Investment	12,118		9,392
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	12,007		9,215
Impaired Financing Receivable, Unpaid Principal Balance	15,097		12,513
Impaired Financing Receivable, Related Allowance	682		305
Financing Receivable, Recorded Investment, Nonaccrual Status	8,180	[1]	6,931	[1]
Impaired Financing Receivable, Interest Income, Accrual Method	315		185
Agriculture Storage and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	4,695		6,319
Impaired Financing Receivable, Recorded Investment	4,337		5,842
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	4,337		5,842
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	4,337		5,842
Impaired Financing Receivable, Unpaid Principal Balance	4,337		5,842
Impaired Financing Receivable, Related Allowance	3,400		1,850
Financing Receivable, Recorded Investment, Nonaccrual Status	4,337	[1]	0	[1]
Impaired Financing Receivable, Interest Income, Accrual Method	0		377
Other Commodity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired Financing Receivable, Average Recorded Investment	1,033		824
Impaired Financing Receivable, Recorded Investment	1,024		1,035
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	907		914
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	901		902
Impaired Financing Receivable, with Related Allowance, Recorded Investment	117		121
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	114		120
Impaired Financing Receivable, Unpaid Principal Balance	1,015		1,022
Impaired Financing Receivable, Related Allowance	1		0
Financing Receivable, Recorded Investment, Nonaccrual Status	0	[1]	0	[1]
Impaired Financing Receivable, Interest Income, Accrual Method	0		0
Less than 90 days past due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 15,700	[1]	$ 12,100	[1]

[1] Includes $15.7 million of loans that are less than 90 days delinquent but which have not met Farmer Mac's performance criteria for returning to accrual status.