Fair Value Disclosures - Quantitative Information (Details) - Fair Value, Measurements, Recurring [Member] - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Institutional Credit [Member] | Cost Approach Valuation Technique [Member] | Farmer Mac Guaranteed Securities [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Available-for-sale, at fair value |
$ 4,121,244
|
$ 3,631,662
|
| USDA Guarantees [Member] | Cost Approach Valuation Technique [Member] | Farmer Mac Guaranteed Securities [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Available-for-sale, at fair value |
31,361
|
27,619
|
| USDA Guarantees [Member] | Cost Approach Valuation Technique [Member] | USDA Securities [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Marketable Securities |
1,917,319
|
1,771,532
|
| Floating Interest Rate [Member] | Market Approach Valuation Technique [Member] | Floating rate auction-rate certificates backed by Government guaranteed student loans |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Available-for-sale, at fair value |
44,924
|
40,576
|
| Floating Interest Rate [Member] | Cost Approach Valuation Technique [Member] | Asset-backed Securities [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Trading, at fair value |
$ 491
|
$ 689
|
| Floating Interest Rate [Member] | Cost Approach Valuation Technique [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Prepayment Rate |
10.00%
|
10.00%
|
| Minimum [Member] | Market Approach Valuation Technique [Member] | Floating rate auction-rate certificates backed by Government guaranteed student loans | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Range of Offered Quotes |
92.00%
|
82.00%
|
| Minimum [Member] | Cost Approach Valuation Technique [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
18.30%
|
14.30%
|
| Minimum [Member] | Institutional Credit [Member] | Cost Approach Valuation Technique [Member] | Farmer Mac Guaranteed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
1.10%
|
0.70%
|
| Minimum [Member] | Institutional Credit [Member] | Cost Approach Valuation Technique [Member] | USDA Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
1.00%
|
0.80%
|
| Fair Value Inputs, Prepayment Rate |
9.00%
|
0.00%
|
| Minimum [Member] | USDA Guarantees [Member] | Cost Approach Valuation Technique [Member] | USDA Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
1.30%
|
1.10%
|
| Fair Value Inputs, Prepayment Rate |
0.00%
|
0.00%
|
| Maximum [Member] | Market Approach Valuation Technique [Member] | Floating rate auction-rate certificates backed by Government guaranteed student loans | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Range of Offered Quotes |
99.60%
|
94.00%
|
| Maximum [Member] | Cost Approach Valuation Technique [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
23.90%
|
23.90%
|
| Maximum [Member] | Institutional Credit [Member] | Cost Approach Valuation Technique [Member] | Farmer Mac Guaranteed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
3.30%
|
2.70%
|
| Maximum [Member] | Institutional Credit [Member] | Cost Approach Valuation Technique [Member] | USDA Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
3.90%
|
3.60%
|
| Fair Value Inputs, Prepayment Rate |
20.00%
|
21.00%
|
| Maximum [Member] | USDA Guarantees [Member] | Cost Approach Valuation Technique [Member] | USDA Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
5.10%
|
5.30%
|
| Fair Value Inputs, Prepayment Rate |
19.00%
|
20.00%
|
| Weighted Average [Member] | Market Approach Valuation Technique [Member] | Floating rate auction-rate certificates backed by Government guaranteed student loans | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Range of Offered Quotes |
96.60%
|
87.10%
|
| Weighted Average [Member] | Cost Approach Valuation Technique [Member] | Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
21.50%
|
19.10%
|
| Weighted Average [Member] | Institutional Credit [Member] | Cost Approach Valuation Technique [Member] | Farmer Mac Guaranteed Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
1.80%
|
1.30%
|
| Weighted Average [Member] | Institutional Credit [Member] | Cost Approach Valuation Technique [Member] | USDA Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
1.80%
|
1.90%
|
| Fair Value Inputs, Prepayment Rate |
10.00%
|
9.00%
|
| Weighted Average [Member] | USDA Guarantees [Member] | Cost Approach Valuation Technique [Member] | USDA Securities [Member] | Fair Value, Inputs, Level 3 [Member] |
|
|
| Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
|
|
| Fair Value Inputs, Discount Rate |
3.10%
|
3.20%
|
| Fair Value Inputs, Prepayment Rate |
7.00%
|
8.00%
|