Fair Value Disclosures - Fair Value Measurements, Recurring and Nonrecurring (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial derivatives	$ 7,834	$ 5,709
Financial derivatives	105,087	27,385
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	8,913	9,999
Financial derivatives	10,519	7,487
Total Assets at fair value	10,122,300	8,209,835
Financial derivatives	27,042	19,633
Total Liabilities at fair value	27,042	19,633
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	0	0
Financial derivatives	0	0
Total Assets at fair value	1,296,923	792,602
Financial derivatives	51	188
Total Liabilities at fair value	51	188
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	0	0
Financial derivatives	10,519	7,487
Total Assets at fair value	1,654,527	1,414,022
Financial derivatives	26,991	19,445
Total Liabilities at fair value	26,991	19,445
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	8,913	9,999
Financial derivatives	0	0
Total Assets at fair value	7,170,850	6,003,211
Financial derivatives	0	0
Total Liabilities at fair value	0	0
Debt Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	2,959,843	2,217,852
Debt Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	1,296,923	792,602
Debt Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	1,644,008	1,406,535
Debt Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	18,912	18,715
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | Institutional Credit | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	7,143,025	5,974,497
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | Institutional Credit | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | Institutional Credit | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | Institutional Credit | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	7,143,025	5,974,497
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | USDA Guarantees | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	7,143,025	5,974,497
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | USDA Guarantees | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | USDA Guarantees | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Farmer Mac Guaranteed Securities | Available-for-Sale Securities | USDA Guarantees | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	7,143,025	5,974,497
USDA Securities: | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	8,913	9,999
USDA Securities: | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	0	0
USDA Securities: | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	0	0
USDA Securities: | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	8,913	9,999
Floating Interest Rate | Floating rate auction-rate certificates backed by Government guaranteed student loans | Available-for-Sale Securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	18,912	18,715
Floating Interest Rate | Floating rate auction-rate certificates backed by Government guaranteed student loans | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Floating Interest Rate | Floating rate auction-rate certificates backed by Government guaranteed student loans | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Floating Interest Rate | Floating rate auction-rate certificates backed by Government guaranteed student loans | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	18,912	18,715
Floating Interest Rate | Floating rate asset-backed securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	11,085	28,678
Floating Interest Rate | Floating rate asset-backed securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Floating Interest Rate | Floating rate asset-backed securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	11,085	28,678
Floating Interest Rate | Floating rate asset-backed securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Floating Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	1,632,583	1,377,454
Floating Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Floating Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	1,632,583	1,377,454
Floating Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Fixed Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	340	403
Fixed Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Fixed Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	340	403
Fixed Interest Rate | Government/GSE Guaranteed Mortgage Backed Securities | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Fixed Interest Rate | Fixed rate U.S. Treasuries | Available-for-Sale Securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	1,296,923	792,602
Fixed Interest Rate | Fixed rate U.S. Treasuries | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	1,296,923	792,602
Fixed Interest Rate | Fixed rate U.S. Treasuries | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	0	0
Fixed Interest Rate | Fixed rate U.S. Treasuries | Available-for-Sale Securities | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities fair value	$ 0	$ 0