Fair Value Disclosures - Fair Value Measurements, Recurring and Nonrecurring (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets:
Financial derivatives	$ 15,088	$ 7,834
Liabilities:
Financial derivatives	200,750	105,087
Debt Securities
Assets:
Available-for-sale, at fair value	3,467,378	2,959,843
Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	7,898,387
Fair Value, Measurements, Recurring
Assets:
Trading	7,786	8,913
Financial derivatives	16,588	10,519
Total Assets at fair value	11,390,139	10,122,300
Liabilities:
Financial derivatives	47,543	27,042
Total Liabilities at fair value	47,543	27,042
Fair Value, Measurements, Recurring \| USDA Securities:
Assets:
Trading	7,786	8,913
Fair Value, Measurements, Recurring \| Debt Securities
Assets:
Available-for-sale, at fair value	3,467,378	2,959,843
Fair Value, Measurements, Recurring \| Level 1
Assets:
Trading	0	0
Financial derivatives	0	0
Total Assets at fair value	1,326,589	1,296,923
Liabilities:
Financial derivatives	9	51
Total Liabilities at fair value	9	51
Fair Value, Measurements, Recurring \| Level 1 \| USDA Securities:
Assets:
Trading	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Debt Securities
Assets:
Available-for-sale, at fair value	1,326,589	1,296,923
Fair Value, Measurements, Recurring \| Level 2
Assets:
Trading	0	0
Financial derivatives	16,588	10,519
Total Assets at fair value	2,139,094	1,654,527
Liabilities:
Financial derivatives	47,534	26,991
Total Liabilities at fair value	47,534	26,991
Fair Value, Measurements, Recurring \| Level 2 \| USDA Securities:
Assets:
Trading	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Debt Securities
Assets:
Available-for-sale, at fair value	2,122,506	1,644,008
Fair Value, Measurements, Recurring \| Level 3
Assets:
Trading	7,786	8,913
Financial derivatives	0	0
Total Assets at fair value	7,924,456	7,170,850
Liabilities:
Financial derivatives	0	0
Total Liabilities at fair value	0	0
Fair Value, Measurements, Recurring \| Level 3 \| USDA Securities:
Assets:
Trading	7,786	8,913
Fair Value, Measurements, Recurring \| Level 3 \| Debt Securities
Assets:
Available-for-sale, at fair value	18,283	18,912
Institutional Credit \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	7,898,387	7,143,025
Institutional Credit \| Fair Value, Measurements, Recurring \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	7,898,387	7,143,025
Institutional Credit \| Fair Value, Measurements, Recurring \| Level 1 \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	0	0
Institutional Credit \| Fair Value, Measurements, Recurring \| Level 2 \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	0	0
Institutional Credit \| Fair Value, Measurements, Recurring \| Level 3 \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	7,898,387	7,143,025
USDA Guarantees \| Fair Value, Measurements, Recurring \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	7,898,387	7,143,025
USDA Guarantees \| Fair Value, Measurements, Recurring \| Level 1 \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	0	0
USDA Guarantees \| Fair Value, Measurements, Recurring \| Level 2 \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	0	0
USDA Guarantees \| Fair Value, Measurements, Recurring \| Level 3 \| Farmer Mac Guaranteed Securities
Assets:
Available-for-sale, at fair value	7,898,387	7,143,025
Floating Interest Rate \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Available-for-sale, at fair value	18,283	18,912
Floating Interest Rate \| Floating rate asset-backed securities
Assets:
Available-for-sale, at fair value	9,807	11,085
Floating Interest Rate \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	2,112,377	1,632,583
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Available-for-sale, at fair value	18,283	18,912
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Floating rate asset-backed securities
Assets:
Available-for-sale, at fair value	9,807	11,085
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	2,112,377	1,632,583
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 1 \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Available-for-sale, at fair value	0	0
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 1 \| Floating rate asset-backed securities
Assets:
Available-for-sale, at fair value	0	0
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 1 \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	0	0
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 2 \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Available-for-sale, at fair value	0	0
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 2 \| Floating rate asset-backed securities
Assets:
Available-for-sale, at fair value	9,807	11,085
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 2 \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	2,112,377	1,632,583
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 3 \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Available-for-sale, at fair value	18,283	18,912
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 3 \| Floating rate asset-backed securities
Assets:
Available-for-sale, at fair value	0	0
Floating Interest Rate \| Fair Value, Measurements, Recurring \| Level 3 \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	0	0
Fixed Interest Rate \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	322	340
Fixed Interest Rate \| Fixed rate U.S. Treasuries
Assets:
Available-for-sale, at fair value	1,326,589	1,296,923
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	322	340
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Fixed rate U.S. Treasuries
Assets:
Available-for-sale, at fair value	1,326,589	1,296,923
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Level 1 \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	0	0
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Level 1 \| Fixed rate U.S. Treasuries
Assets:
Available-for-sale, at fair value	1,326,589	1,296,923
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Level 2 \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	322	340
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Level 2 \| Fixed rate U.S. Treasuries
Assets:
Available-for-sale, at fair value	0	0
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Level 3 \| Government/GSE Guaranteed Mortgage Backed Securities
Assets:
Available-for-sale, at fair value	0	0
Fixed Interest Rate \| Fair Value, Measurements, Recurring \| Level 3 \| Fixed rate U.S. Treasuries
Assets:
Available-for-sale, at fair value	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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