Financial Derivatives - Schedule of Net Income/(Expense) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Investments and cash equivalents	$ 4,457	$ 10,399	$ 9,986	$ 28,140
Interest Income Farmer Mac Guaranteed Securities and USDA Securities	42,414	61,792	84,818	133,309
Interest Income Loans	60,214	55,430	119,708	116,026
Total interest expense	(51,956)	(79,273)	(106,132)	(187,815)
(Losses)/gains on financial derivatives	(3,066)	6,523	1,227	(2,775)
Total amounts presented in the consolidated statement of operations	52,063	44,472	109,607	58,745
Interest expense on interest rate swaps	526	11,271	9,363	6,183
Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	114,935	9,739	(169,112)	384,962
Gains/(losses) on fair value hedging relationships	(1,725)	(2,381)	(1,379)	(8,062)
Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	(8)	(2)	(15)	(2)
Interest settlements reclassified from AOCI into net income on derivatives	(1,776)	(1,563)	(3,523)	(2,002)
Recognized on hedged items	(643)	(1,029)	(1,298)	(3,152)
Expense recognized on cash flow hedges	(2,427)	(2,594)	(4,836)	(5,156)
Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	30,126	29,193	60,581	55,419
Discount amortization recognized on hedged items	(257)	(181)	(478)	(361)
No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	(3,066)	6,523	1,227	(2,775)
Interest Income Investments and Cash Equivalents | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	188		188
Gains/(losses) on fair value hedging relationships	12		12
Interest Income Investments and Cash Equivalents | 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 Investments and Cash Equivalents | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	67		67
Discount amortization recognized on hedged items	0		0
Interest Income Investments and Cash Equivalents | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0		0
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	49,878	9,050	(118,922)	299,430
Gains/(losses) on fair value hedging relationships	1,198	(176)	474	(3,729)
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	0	0
Interest settlements reclassified from AOCI into net income on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Expense recognized on cash flow hedges	0	0	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	30,565	32,102	61,341	63,927
Discount amortization recognized on hedged items	0	0	0	0
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	63,978	3,037	(80,770)	148,445
Gains/(losses) on fair value hedging relationships	(1,169)	(3,579)	(146)	(4,076)
Interest Income Loans | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	0	0	0	0
Interest settlements reclassified from AOCI into net income on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Expense recognized on cash flow hedges	0	0	0	0
Interest Income Loans | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	11,635	9,812	23,122	18,489
Discount amortization recognized on hedged items	0	0	0	0
Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	891	(2,348)	30,392	(62,913)
Gains/(losses) on fair value hedging relationships	(1,766)	1,374	(1,719)	(257)
Total Interest Expense | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	(8)	(2)	(15)	(2)
Interest settlements reclassified from AOCI into net income on derivatives	(1,776)	(1,563)	(3,523)	(2,002)
Recognized on hedged items	(643)	(1,029)	(1,298)	(3,152)
Expense recognized on cash flow hedges	(2,427)	(2,594)	(4,836)	(5,156)
Total Interest Expense | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	(12,141)	(12,721)	(23,949)	(26,997)
Discount amortization recognized on hedged items	(257)	(181)	(478)	(361)
Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Losses on financial derivatives | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	0	0	0	0
Gains/(losses) on fair value hedging relationships	0	0	0	0
Losses on financial derivatives | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	0	0	0	0
Interest settlements reclassified from AOCI into net income on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Expense recognized on cash flow hedges	0	0	0	0
Losses on financial derivatives | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	0	0	0	0
Discount amortization recognized on hedged items	0	0	0	0
Losses on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	(3,066)	6,523	1,227	(2,775)
Interest Rate Swap | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(18,532)	(11,360)	(37,059)	(17,754)
Income/(expense) related to interest settlements on fair value hedging relationships	11,337	17,652	23,044	37,304
Recognized on derivatives	(116,660)	(12,120)	167,733	(393,024)
Interest Rate Swap | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	(3,739)	8,427	(2,271)	1,878
Interest expense on interest rate swaps	1,098	(1,795)	3,322	(2,657)
Interest Rate Swap | Interest Income Investments and Cash Equivalents | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(35)		(35)
Income/(expense) related to interest settlements on fair value hedging relationships	32		32
Recognized on derivatives	(176)		(176)
Interest Rate Swap | Interest Income Investments and Cash Equivalents | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0		0
Interest expense on interest rate swaps	0		0
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(21,604)	(12,257)	(43,041)	(18,408)
Income/(expense) related to interest settlements on fair value hedging relationships	8,961	19,845	18,300	45,519
Recognized on derivatives	(48,680)	(9,226)	119,396	(303,159)
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Interest expense on interest rate swaps	0	0	0	0
Interest Rate Swap | Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(6,704)	(4,535)	(13,275)	(6,412)
Income/(expense) related to interest settlements on fair value hedging relationships	4,931	5,277	9,847	12,077
Recognized on derivatives	(65,147)	(6,616)	80,624	(152,521)
Interest Rate Swap | Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Interest expense on interest rate swaps	0	0	0	0
Interest Rate Swap | Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	9,811	5,432	19,292	7,066
Income/(expense) related to interest settlements on fair value hedging relationships	(2,587)	(7,470)	(5,135)	(20,292)
Recognized on derivatives	(2,657)	3,722	(32,111)	62,656
Interest Rate Swap | Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Interest expense on interest rate swaps	0	0	0	0
Interest Rate Swap | Losses on financial derivatives | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	0	0	0	0
Income/(expense) related to interest settlements on fair value hedging relationships	0	0	0	0
Recognized on derivatives	0	0	0	0
Interest Rate Swap | Losses on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	(3,739)	8,427	(2,271)	1,878
Interest expense on interest rate swaps	1,098	(1,795)	3,322	(2,657)
Treasury futures | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	(425)	(109)	176	(1,996)
Treasury futures | Interest Income Investments and Cash Equivalents | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0		0
Treasury futures | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Treasury futures | Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Treasury futures | Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	0	0	0	0
Treasury futures | Losses on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives	$ (425)	$ (109)	$ 176	$ (1,996)