Summary of Significant Accounting Policies - Consolidation of Variable Interest Entities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Loans held for investment, at amortized cost	$ 7,341,912	$ 7,261,933
Debt securities of consolidated trusts held by third parties	21,536,571	21,795,677
Farmer Mac Guaranteed Securities
Variable Interest Entity [Line Items]
Fair Value	6,763,209	6,947,701
Investment securities:
Variable Interest Entity [Line Items]
Fair Value	3,809,632	3,853,692
Unamortized Premium/(Discount)	0	0
On-Balance Sheet: \| Consolidated VIE
Variable Interest Entity [Line Items]
Loans held for investment, at amortized cost	1,174,525	1,287,045
Debt securities of consolidated trusts held by third parties	1,188,521	1,323,786
On-Balance Sheet: \| Farmer Mac Guaranteed Securities \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	32,128	34,537
Maximum exposure to loss	32,050	34,456
On-Balance Sheet: \| Investment securities: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	1,963,903	1,918,672
Maximum exposure to loss	1,954,583	1,909,535
Off-Balance Sheet: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Maximum exposure to loss	357,071	378,610
Farm & Ranch
Variable Interest Entity [Line Items]
Loans held for investment, at amortized cost	6,302,967	6,176,438
Borrower remittances	14,000	36,700
USDA Guarantees
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	100	100
Operating Segments \| Farm & Ranch \| On-Balance Sheet: \| Consolidated VIE
Variable Interest Entity [Line Items]
Loans held for investment, at amortized cost	1,174,525	1,287,045
Debt securities of consolidated trusts held by third parties	1,188,521	1,323,786
Operating Segments \| Farm & Ranch \| On-Balance Sheet: \| Farmer Mac Guaranteed Securities \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	0	0
Maximum exposure to loss	0	0
Operating Segments \| Farm & Ranch \| On-Balance Sheet: \| Investment securities: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	0	0
Maximum exposure to loss	0	0
Operating Segments \| Farm & Ranch \| Off-Balance Sheet: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Maximum exposure to loss	72,203	79,312
Operating Segments \| USDA Guarantees \| On-Balance Sheet: \| Consolidated VIE
Variable Interest Entity [Line Items]
Loans held for investment, at amortized cost	0	0
Debt securities of consolidated trusts held by third parties	0	0
Operating Segments \| USDA Guarantees \| On-Balance Sheet: \| Farmer Mac Guaranteed Securities \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	32,128	34,537
Maximum exposure to loss	32,050	34,456
Operating Segments \| USDA Guarantees \| On-Balance Sheet: \| Investment securities: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	0	0
Maximum exposure to loss	0	0
Operating Segments \| USDA Guarantees \| Off-Balance Sheet: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Maximum exposure to loss	284,868	299,298
Corporate \| On-Balance Sheet: \| Consolidated VIE
Variable Interest Entity [Line Items]
Loans held for investment, at amortized cost	0	0
Debt securities of consolidated trusts held by third parties	0	0
Corporate \| On-Balance Sheet: \| Farmer Mac Guaranteed Securities \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	0	0
Maximum exposure to loss	0	0
Corporate \| On-Balance Sheet: \| Investment securities: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Fair Value	1,963,903	1,918,672
Maximum exposure to loss	1,954,583	1,909,535
Corporate \| Off-Balance Sheet: \| Unconsolidated VIE
Variable Interest Entity [Line Items]
Maximum exposure to loss	$ 0	$ 0

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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