Investment Securities - Investment Securities (Tables) - Investment Securities [Member]
 12 Months Ended
Dec. 31, 2015
Schedule of Available-for-sale and Trading Securities [Line Items]  
Marketable Securities [Table Text Block]
The following tables set forth information about Farmer Mac's investment securities as of December 31, 2015 and 2014:
 
Table 4.1

 
As of December 31, 2015
 
Amount Outstanding
 
Unamortized Premium/(Discount)
 
Amortized
Cost
 
Unrealized
Gains
 
Unrealized
Losses
 
Fair Value
 
(in thousands)
Available-for-sale:
 
 
 
 
 
 
 
 
 
 
 
Floating rate auction-rate certificates backed by Government guaranteed student loans
$
46,500

 
$
—

 
$
46,500

 
$
—

 
$
(1,576
)
 
$
44,924

Floating rate asset-backed securities
74,744

 
(253
)
 
74,491

 
14

 
(776
)
 
73,729

Floating rate corporate debt securities
10,000

 
—

 
10,000

 
—

 
(9
)
 
9,991

Fixed rate corporate debt securities
10,000

 
(1
)
 
9,999

 
—

 
(5
)
 
9,994

Floating rate Government/GSE guaranteed mortgage-backed securities
1,353,495

 
3,515

 
1,357,010

 
2,768

 
(4,319
)
 
1,355,459

Fixed rate GSE guaranteed mortgage-backed securities(1)
692

 
3,117

 
3,809

 
4,095

 
—

 
7,904

Floating rate GSE subordinated debt
70,000

 
—

 
70,000

 
—

 
(3,751
)
 
66,249

Fixed rate senior agency debt
214,000

 
(25
)
 
213,975

 
12

 
—

 
213,987

Fixed rate U.S. Treasuries
993,680

 
(417
)
 
993,263

 
2

 
(477
)
 
992,788

Total available-for-sale
2,773,111

 
5,936

 
2,779,047

 
6,891

 
(10,913
)
 
2,775,025

Trading:
 
 
 
 
 

 
 

 
 

 
 

Floating rate asset-backed securities
2,211

 
—

 
2,211

 
—

 
(1,720
)
 
491

Total investment securities
$
2,775,322

 
$
5,936

 
$
2,781,258

 
$
6,891

 
$
(12,633
)
 
$
2,775,516

(1) 
Fair value includes $7.2 million of an interest-only security with a notional amount of $148.5 million.






 
As of December 31, 2014
 
Amount Outstanding
 
Unamortized Premium/(Discount)
 
Amortized
Cost
 
Unrealized
Gains
 
Unrealized
Losses
 
Fair Value
 
(in thousands)
Available-for-sale:
 
 
 
 
 
 
 
 
 
 
 
Floating rate auction-rate certificates backed by Government guaranteed student loans
$
46,600

 
$
—

 
$
46,600

 
$
—

 
$
(6,024
)
 
$
40,576

Floating rate asset-backed securities
100,730

 
(74
)
 
100,656

 
283

 
(37
)
 
100,902

Floating rate corporate debt securities
10,000

 
—

 
10,000

 
91

 
—

 
10,091

Fixed rate corporate debt securities
30,000

 
(10
)
 
29,990

 
35

 
—

 
30,025

Floating rate Government/GSE guaranteed mortgage-backed securities
605,053

 
3,431

 
608,484

 
4,712

 
(443
)
 
612,753

Fixed rate GSE guaranteed mortgage-backed securities(1)
853

 
3,542

 
4,395

 
3,807

 
—

 
8,202

Floating rate GSE subordinated debt
70,000

 
—

 
70,000

 
—

 
(3,680
)
 
66,320

Fixed rate senior agency debt
18,806

 
130

 
18,936

 
3

 
—

 
18,939

Floating rate U.S. Treasuries
75,000

 
(10
)
 
74,990

 
—

 
(11
)
 
74,979

Fixed rate U.S. Treasuries
975,194

 
462

 
975,656

 
72

 
(16
)
 
975,712

Total available-for-sale
1,932,236

 
7,471

 
1,939,707

 
9,003

 
(10,211
)
 
1,938,499

Trading:
 
 
 
 
 

 
 

 
 

 
 

Floating rate asset-backed securities
2,868

 
—

 
2,868

 
—

 
(2,179
)
 
689

Total investment securities
$
1,935,104

 
$
7,471

 
$
1,942,575

 
$
9,003

 
$
(12,390
)
 
$
1,939,188

(1) 
Fair value includes $7.3 million of an interest-only security with a notional amount of $152.4 million.
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block]
As of December 31, 2015 and 2014, unrealized losses on available-for-sale investment securities were as follows:

Table 4.2

 
As of December 31, 2015
 
Available-for-Sale Securities
 
Unrealized loss position for
less than 12 months
 
Unrealized loss position for
more than 12 months
 
Fair Value
 
Unrealized
Loss
 
Fair Value
 
Unrealized
Loss
 
(in thousands)
Floating rate auction-rate certificates backed by Government guaranteed student loans
$
—

 
$
—

 
$
18,124

 
$
(1,576
)
Floating rate asset-backed securities
44,552

 
(464
)
 
9,975

 
(312
)
Floating rate corporate debt securities
4,991

 
(9
)
 
—

 
—

Fixed rate corporate debt securities
9,994

 
(5
)
 
—

 
—

Floating rate Government/GSE guaranteed mortgage-backed securities
794,959

 
(3,408
)
 
100,192

 
(911
)
Floating rate GSE subordinated debt
—

 
—

 
66,249

 
(3,751
)
Fixed rate U.S. Treasuries
944,842

 
(477
)
 
—

 
—

Total
$
1,799,338

 
$
(4,363
)
 
$
194,540

 
$
(6,550
)

 
As of December 31, 2014
 
Available-for-Sale Securities
 
Unrealized loss position for
less than 12 months
 
Unrealized loss position for
more than 12 months
 
Fair Value
 
Unrealized
Loss
 
Fair Value
 
Unrealized
Loss
 
(in thousands)
Floating rate auction-rate certificates backed by Government guaranteed student loans
$
—

 
$
—

 
$
40,576

 
$
(6,024
)
Floating rate asset-backed securities
19,388

 
(37
)
 
—

 
—

Floating rate Government/GSE guaranteed mortgage-backed securities
76,100

 
(164
)
 
76,867

 
(279
)
Floating rate GSE subordinated debt
—

 
—

 
66,320

 
(3,680
)
Floating rate U.S. Treasuries
74,980

 
(11
)
 
—

 
—

Fixed rate U.S. Treasuries
325,033

 
(16
)
 
—

 
—

Total
$
495,501

 
$
(228
)
 
$
183,763

 
$
(9,983
)

The unrealized losses presented above are principally due to a general widening of credit spreads from the dates of acquisition to December 31, 2015 and 2014, as applicable. The resulting decrease in fair values reflects an increase in the perceived risk by the financial markets related to those securities. As of December 31, 2015, all of the investment securities in an unrealized loss position either were backed by the full faith and credit of the U.S. government or had credit ratings of at least "AA+," except three that were rated "A-." As of December 31, 2014 , all of the investment securities in an unrealized loss position either were backed by the full faith and credit of the U.S. government or had credit ratings of at least "AA+," except one that was rated "A-." The unrealized losses were on 69 and 35 individual investment securities as of December 31, 2015 and 2014, respectively.

As of December 31, 2015, 17 of the securities in loss positions had been in loss positions for more than 12 months and had a total unrealized loss of $6.6 million. As of December 31, 2014, 15 of the securities in loss positions had been in loss positions for more than 12 months and had a total unrealized loss of $10.0 million.  Securities in unrealized loss positions for 12 months or longer have a fair value as of December 31, 2015 that is, on average, approximately 97 percent of their amortized cost basis. Farmer Mac believes that all of these unrealized losses are recoverable within a reasonable period of time by way of maturity or changes in credit spreads. Accordingly, Farmer Mac has concluded that none of the unrealized losses on these available-for-sale investment securities represents other-than-temporary impairment as of December 31, 2015 and 2014.
Investments Classified by Contractual Maturity Date [Table Text Block]

The amortized cost, fair value, and weighted average yield of available-for-sale investment securities by remaining contractual maturity as of December 31, 2015 are set forth below. Asset-backed and mortgage-backed securities are included based on their final maturities, although the actual maturities may differ due to prepayments of the underlying assets.

Table 4.3

 
As of December 31, 2015
 
Available-for-Sale Securities
 
Amortized
Cost
 
Fair Value
 
Weighted-
Average
Yield
 
(dollars in thousands)
Due within one year
$
1,222,236

 
$
1,221,760

 
0.43%
Due after one year through five years
146,389

 
147,101

 
1.10%
Due after five years through ten years
575,023

 
573,082

 
0.86%
Due after ten years
835,399

 
833,082

 
0.90%
Total
$
2,779,047

 
$
2,775,025

 
0.70%