Fair Value Disclosures - Fair Value Measurements, Recurring and Nonrecurring (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Financial derivatives	$ 13,453	$ 16,123
Liabilities:
Financial derivatives	169,814	182,371
Investment securities:
Assets:
Fair Value	3,809,632	$ 3,853,692
Farmer Mac Guaranteed Securities
Assets:
Fair Value	$ 6,763,209
Level 3
Liabilities:
Percent of level three fair value assets and liabilities	28.00%	29.00%
Financial instruments level three percent	64.00%	65.00%
Recurring
Assets:
Financial derivatives	$ 18,370	$ 17,468
Total Assets at fair value	10,596,789	10,825,556
Liabilities:
Financial derivatives	28,345	29,892
Total Liabilities at fair value	28,345	29,892
Recurring \| USDA Securities:
Assets:
Trading	5,578	6,695
Recurring \| Investment securities:
Assets:
Fair Value	3,809,632	3,853,692
Recurring \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	6,763,209	6,947,701
Recurring \| Level 1
Assets:
Financial derivatives	20	0
Total Assets at fair value	1,402,747	1,467,951
Liabilities:
Financial derivatives	0	82
Total Liabilities at fair value	0	82
Recurring \| Level 1 \| USDA Securities:
Assets:
Trading	0	0
Recurring \| Level 1 \| Investment securities:
Assets:
Fair Value	1,402,727	1,467,951
Recurring \| Level 1 \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	0	0
Recurring \| Level 2
Assets:
Financial derivatives	18,350	17,468
Total Assets at fair value	2,406,109	2,384,038
Liabilities:
Financial derivatives	28,345	29,810
Total Liabilities at fair value	28,345	29,810
Recurring \| Level 2 \| USDA Securities:
Assets:
Trading	0	0
Recurring \| Level 2 \| Investment securities:
Assets:
Fair Value	2,387,759	2,366,570
Recurring \| Level 2 \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	0	0
Recurring \| Level 3
Assets:
Financial derivatives	0	0
Total Assets at fair value	6,787,933	6,973,567
Liabilities:
Financial derivatives	0	0
Total Liabilities at fair value	0	0
Recurring \| Level 3 \| USDA Securities:
Assets:
Trading	5,578	6,695
Recurring \| Level 3 \| Investment securities:
Assets:
Fair Value	19,146	19,171
Recurring \| Level 3 \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	6,763,209	6,947,701
AgVantage Securities \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	6,763,209	6,947,701
AgVantage Securities \| Recurring \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	6,763,209	6,947,701
AgVantage Securities \| Recurring \| Level 1 \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	0	0
AgVantage Securities \| Recurring \| Level 2 \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	0	0
AgVantage Securities \| Recurring \| Level 3 \| Farmer Mac Guaranteed Securities
Assets:
Fair Value	6,763,209	6,947,701
USDA Guarantees \| Recurring \| USDA Securities:
Assets:
Trading	5,578	6,695
USDA Guarantees \| Recurring \| Level 1 \| USDA Securities:
Assets:
Trading	0	0
USDA Guarantees \| Recurring \| Level 2 \| USDA Securities:
Assets:
Trading	0	0
USDA Guarantees \| Recurring \| Level 3 \| USDA Securities:
Assets:
Trading	5,578	6,695
Floating Interest Rate \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Fair Value	19,146	19,171
Floating Interest Rate \| Floating rate asset-backed securities
Assets:
Fair Value		6,231
Floating Interest Rate \| Guaranteed mortgage-backed securities
Assets:
Fair Value	2,387,558	2,360,026
Floating Interest Rate \| Recurring \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Fair Value	19,146	19,171
Floating Interest Rate \| Recurring \| Floating rate asset-backed securities
Assets:
Fair Value		6,231
Floating Interest Rate \| Recurring \| Guaranteed mortgage-backed securities
Assets:
Fair Value	2,387,558	2,360,026
Floating Interest Rate \| Recurring \| Level 1 \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Fair Value	0	0
Floating Interest Rate \| Recurring \| Level 1 \| Floating rate asset-backed securities
Assets:
Fair Value		0
Floating Interest Rate \| Recurring \| Level 1 \| Guaranteed mortgage-backed securities
Assets:
Fair Value	0	0
Floating Interest Rate \| Recurring \| Level 2 \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Fair Value	0	0
Floating Interest Rate \| Recurring \| Level 2 \| Floating rate asset-backed securities
Assets:
Fair Value		6,231
Floating Interest Rate \| Recurring \| Level 2 \| Guaranteed mortgage-backed securities
Assets:
Fair Value	2,387,558	2,360,026
Floating Interest Rate \| Recurring \| Level 3 \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Assets:
Fair Value	19,146	19,171
Floating Interest Rate \| Recurring \| Level 3 \| Floating rate asset-backed securities
Assets:
Fair Value		0
Floating Interest Rate \| Recurring \| Level 3 \| Guaranteed mortgage-backed securities
Assets:
Fair Value	0	0
Fixed Interest Rate \| Guaranteed mortgage-backed securities
Assets:
Fair Value	201	313
Fixed Interest Rate \| Fixed rate U.S. Treasuries
Assets:
Fair Value	1,402,727	1,467,951
Fixed Interest Rate \| Recurring \| Guaranteed mortgage-backed securities
Assets:
Fair Value	201	313
Fixed Interest Rate \| Recurring \| Fixed rate U.S. Treasuries
Assets:
Fair Value	1,402,727	1,467,951
Fixed Interest Rate \| Recurring \| Level 1 \| Guaranteed mortgage-backed securities
Assets:
Fair Value	0	0
Fixed Interest Rate \| Recurring \| Level 1 \| Fixed rate U.S. Treasuries
Assets:
Fair Value	1,402,727	1,467,951
Fixed Interest Rate \| Recurring \| Level 2 \| Guaranteed mortgage-backed securities
Assets:
Fair Value	201	313
Fixed Interest Rate \| Recurring \| Level 2 \| Fixed rate U.S. Treasuries
Assets:
Fair Value	0	0
Fixed Interest Rate \| Recurring \| Level 3 \| Guaranteed mortgage-backed securities
Assets:
Fair Value	0	0
Fixed Interest Rate \| Recurring \| Level 3 \| Fixed rate U.S. Treasuries
Assets:
Fair Value	$ 0	$ 0

Fair Value, Assets and Liabilities Fair Value as Percent of Total Assets

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Fair Value, Assets and Liabilities, Fair Value as Percent of Total Financial Instruments Measured at Fair Value

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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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