Loans and Allowance for Losses and Concentrations of Credit Risk - Allowance for Losses by Impairment Method and Commodity (Details) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment $ 5,649,604 $ 5,334,737    
Financing Receivable, Individually Evaluated for Impairment 75,695 82,437    
Financing Receivable, Gross [1],[2] 5,725,299 5,417,174    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 4,713 7,490    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 1,850 2,637    
Financing Receivable, Allowance for Credit Losses 6,563 10,127 $ 13,334 $ 16,890
Crops [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 3,224,911 2,926,501    
Financing Receivable, Individually Evaluated for Impairment 18,740 14,765    
Financing Receivable, Gross [1] 3,243,651 2,941,266    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 2,315 2,122    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 476 397    
Financing Receivable, Allowance for Credit Losses 2,791 2,519 2,124  
Permanent Plantings [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 917,127 881,052    
Financing Receivable, Individually Evaluated for Impairment 24,284 39,143    
Financing Receivable, Gross [1] 941,411 920,195    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 571 644    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 360 1,515    
Financing Receivable, Allowance for Credit Losses 931 2,159 2,186  
Livestock [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 1,221,983 1,245,335    
Financing Receivable, Individually Evaluated for Impairment 14,798 15,283    
Financing Receivable, Gross [1] 1,236,781 1,260,618    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 994 1,062    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 787 361    
Financing Receivable, Allowance for Credit Losses 1,781 1,423 1,271  
Part-Time Farm [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 203,090 160,708    
Financing Receivable, Individually Evaluated for Impairment 8,035 13,246    
Financing Receivable, Gross [1] 211,125 173,954    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 181 103    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 227 364    
Financing Receivable, Allowance for Credit Losses 408 467 454  
Agriculture Storage and Processing [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 72,152 114,360    
Financing Receivable, Individually Evaluated for Impairment 9,838 0    
Financing Receivable, Gross [1] 81,990 114,360    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 649 3,552    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 0 0    
Financing Receivable, Allowance for Credit Losses 649 3,552 7,292  
Other Commodity [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 10,341 6,781    
Financing Receivable, Individually Evaluated for Impairment 0 0    
Financing Receivable, Gross [1] 10,341 6,781    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 3 7    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 0 0    
Financing Receivable, Allowance for Credit Losses 3 7 $ 7  
On-balance sheet [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 2,900,868 2,473,780    
Financing Receivable, Individually Evaluated for Impairment 57,107 66,442    
Financing Receivable, Gross [1] 2,957,975 2,540,222    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 3,387 3,531    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 1,093 2,333    
Financing Receivable, Allowance for Credit Losses 4,480 5,864    
On-balance sheet [Member] | Crops [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 1,911,039 1,621,360    
Financing Receivable, Individually Evaluated for Impairment 12,803 12,307    
Financing Receivable, Gross [1] 1,923,842 1,633,667    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 1,968 1,824    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 290 283    
Financing Receivable, Allowance for Credit Losses 2,258 2,107    
On-balance sheet [Member] | Permanent Plantings [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 433,654 359,517    
Financing Receivable, Individually Evaluated for Impairment 21,247 35,904    
Financing Receivable, Gross [1] 454,901 395,421    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 434 495    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 218 1,410    
Financing Receivable, Allowance for Credit Losses 652 1,905    
On-balance sheet [Member] | Livestock [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 444,320 406,049    
Financing Receivable, Individually Evaluated for Impairment 5,958 6,571    
Financing Receivable, Gross [1] 450,278 412,620    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 702 658    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 384 328    
Financing Receivable, Allowance for Credit Losses 1,086 986    
On-balance sheet [Member] | Part-Time Farm [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 92,712 57,851    
Financing Receivable, Individually Evaluated for Impairment 7,261 11,660    
Financing Receivable, Gross [1] 99,973 69,511    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 116 51    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 201 312    
Financing Receivable, Allowance for Credit Losses 317 363    
On-balance sheet [Member] | Agriculture Storage and Processing [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 15,944 29,003    
Financing Receivable, Individually Evaluated for Impairment 9,838 0    
Financing Receivable, Gross [1] 25,782 29,003    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 167 503    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 0 0    
Financing Receivable, Allowance for Credit Losses 167 503    
On-balance sheet [Member] | Other Commodity [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 3,199 0    
Financing Receivable, Individually Evaluated for Impairment 0 0    
Financing Receivable, Gross [1] 3,199 0    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 0 0    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 0 0    
Financing Receivable, Allowance for Credit Losses 0 0    
Off-balance sheet [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 2,748,736 2,860,957    
Financing Receivable, Individually Evaluated for Impairment 18,588 15,995    
Financing Receivable, Gross [1] 2,767,324 2,876,952    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 1,326 3,959    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 757 304    
Financing Receivable, Allowance for Credit Losses 2,083 4,263    
Off-balance sheet [Member] | Crops [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 1,313,872 1,305,141    
Financing Receivable, Individually Evaluated for Impairment 5,937 2,458    
Financing Receivable, Gross [1] 1,319,809 1,307,599    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 347 298    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 186 114    
Financing Receivable, Allowance for Credit Losses 533 412    
Off-balance sheet [Member] | Permanent Plantings [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 483,473 521,535    
Financing Receivable, Individually Evaluated for Impairment 3,037 3,239    
Financing Receivable, Gross [1] 486,510 524,774    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 137 149    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 142 105    
Financing Receivable, Allowance for Credit Losses 279 254    
Off-balance sheet [Member] | Livestock [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 777,663 839,286    
Financing Receivable, Individually Evaluated for Impairment 8,840 8,712    
Financing Receivable, Gross [1] 786,503 847,998    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 292 404    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 403 33    
Financing Receivable, Allowance for Credit Losses 695 437    
Off-balance sheet [Member] | Part-Time Farm [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 110,378 102,857    
Financing Receivable, Individually Evaluated for Impairment 774 1,586    
Financing Receivable, Gross [1] 111,152 104,443    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 65 52    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 26 52    
Financing Receivable, Allowance for Credit Losses 91 104    
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 56,208 85,357    
Financing Receivable, Individually Evaluated for Impairment 0 0    
Financing Receivable, Gross [1] 56,208 85,357    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 482 3,049    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 0 0    
Financing Receivable, Allowance for Credit Losses 482 3,049    
Off-balance sheet [Member] | Other Commodity [Member]        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Financing Receivable, Collectively Evaluated for Impairment 7,142 6,781    
Financing Receivable, Individually Evaluated for Impairment 0 0    
Financing Receivable, Gross [1] 7,142 6,781    
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment 3 7    
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment 0 0    
Financing Receivable, Allowance for Credit Losses $ 3 $ 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.
[2] 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).