Financial Derivatives - Schedule of Net Income/(Expense) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income Farmer Mac Guaranteed Securities and USDA Securities	$ 42,404	$ 71,517
Interest Income Loans	59,494	60,596
Total interest expense	(54,176)	(108,542)
Gains/(losses) on financial derivatives	4,293	(9,298)
Total amounts presented in the consolidated statement of operations	52,015	14,273
Interest expense on interest rate swaps	8,837	(5,088)
Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	(284,049)	375,223
(Losses)/gains on fair value hedging relationships	345	(5,681)
Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	(7)	(1)
Interest settlements reclassified from AOCI into net income on derivatives	(1,746)	(439)
Recognized on hedged items	(655)	(2,123)
Expense recognized on cash flow hedges	(2,408)	(2,563)
Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	30,454	26,227
Discount amortization recognized on hedged items	(221)	(180)
No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	4,293	(9,298)
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	(168,801)	290,379
(Losses)/gains on fair value hedging relationships	(723)	(3,553)
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	0	0
Interest settlements reclassified from AOCI into net income on derivatives	0	0
Recognized on hedged items	0	0
Expense recognized on cash flow hedges	0	0
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	30,775	31,826
Discount amortization recognized on hedged items	0	0
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	(144,749)	145,409
(Losses)/gains on fair value hedging relationships	1,022	(497)
Interest Income Loans | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	0	0
Interest settlements reclassified from AOCI into net income on derivatives	0	0
Recognized on hedged items	0	0
Expense recognized on cash flow hedges	0	0
Interest Income Loans | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	11,487	8,677
Discount amortization recognized on hedged items	0	0
Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	29,501	(60,565)
(Losses)/gains on fair value hedging relationships	46	(1,631)
Total Interest Expense | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	(7)	(1)
Interest settlements reclassified from AOCI into net income on derivatives	(1,746)	(439)
Recognized on hedged items	(655)	(2,123)
Expense recognized on cash flow hedges	(2,408)	(2,563)
Total Interest Expense | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	(11,808)	(14,276)
Discount amortization recognized on hedged items	(221)	(180)
Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Gains on financial derivatives | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	0	0
(Losses)/gains on fair value hedging relationships	0	0
Gains on financial derivatives | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	0	0
Interest settlements reclassified from AOCI into net income on derivatives	0	0
Recognized on hedged items	0	0
Expense recognized on cash flow hedges	0	0
Gains on financial derivatives | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	0	0
Discount amortization recognized on hedged items	0	0
Gains on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	4,293	(9,298)
Interest Rate Swap | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(18,528)	(6,395)
Income/(expense) related to interest settlements on fair value hedging relationships	11,705	19,652
Recognized on derivatives	284,394	(380,904)
Interest Rate Swap | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	1,470	(6,550)
Interest expense on interest rate swaps	2,223	(862)
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(21,437)	(6,152)
Income/(expense) related to interest settlements on fair value hedging relationships	9,338	25,674
Recognized on derivatives	168,078	(293,932)
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Interest expense on interest rate swaps	0	0
Interest Rate Swap | Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(6,572)	(1,877)
Income/(expense) related to interest settlements on fair value hedging relationships	4,915	6,800
Recognized on derivatives	145,771	(145,906)
Interest Rate Swap | Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Interest expense on interest rate swaps	0	0
Interest Rate Swap | Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	9,481	1,634
Income/(expense) related to interest settlements on fair value hedging relationships	(2,548)	(12,822)
Recognized on derivatives	(29,455)	58,934
Interest Rate Swap | Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Interest expense on interest rate swaps	0	0
Interest Rate Swap | Gains on financial derivatives | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	0	0
Income/(expense) related to interest settlements on fair value hedging relationships	0	0
Recognized on derivatives	0	0
Interest Rate Swap | Gains on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	1,470	(6,550)
Interest expense on interest rate swaps	2,223	(862)
Treasury futures | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	600	(1,886)
Treasury futures | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Treasury futures | Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Treasury futures | Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	0	0
Treasury futures | Gains on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives	$ 600	$ (1,886)