Financial Derivatives - Schedule of Net Income/(Expense) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income Farmer Mac Guaranteed Securities and USDA Securities		$ 333,896	$ 227,691		$ 290,953
Interest Income Loans		229,675	233,699	$ 229,675	198,152
Total interest expense		(471,958)	(312,946)	(471,958)	(369,848)
(Losses)/gains on financial derivatives		5,282	(246)	5,282	(3,687)
Total amounts presented in the consolidated statement of operations		96,895	148,198		115,570
Interest expense on interest rate swaps			16,053	$ 20,945	11,643
Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	$ 230,330	208,311			19,354
(Losses)/gains on fair value hedging relationships	(9,184)	(7,907)			4,941
Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items		(4)	(13)		(6)
Interest settlements reclassified from AOCI into net income on derivatives		1,166	(5,570)		316
Recognized on hedged items		(10,569)	(4,553)		(9,182)
Expense recognized on cash flow hedges		(9,407)	(10,136)		(8,872)
Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items		99,652	115,733		34,685
Discount amortization recognized on hedged items		631	(745)		668
No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives		5,282	(246)		(3,687)
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items		181,144	202,624		21,460
(Losses)/gains on fair value hedging relationships		(3,334)	(3,657)		1,181
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
Interest settlements reclassified from AOCI into net income on derivatives		0	0		0
Recognized on hedged items		0	0		0
Expense recognized on cash flow hedges		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		118,609	126,170		65,238
Discount amortization recognized on hedged items		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
Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items		43,194	73,426		(5,243)
(Losses)/gains on fair value hedging relationships		(6,947)	(3,139)		(212)
Interest Income Loans | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items		0	0		0
Interest settlements reclassified from AOCI into net income on derivatives		0	0		0
Recognized on hedged items		0	0		0
Expense recognized on cash flow hedges		0	0		0
Interest Income Loans | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items		26,352	40,793		6,284
Discount amortization recognized on hedged items		0	0		0
Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives		0	0		0
Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items		(16,027)	(45,720)		3,137
(Losses)/gains on fair value hedging relationships		2,374	(2,388)		3,972
Total Interest Expense | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items		(4)	(13)		(6)
Interest settlements reclassified from AOCI into net income on derivatives		1,166	(5,570)		316
Recognized on hedged items		(10,569)	(4,553)		(9,182)
Expense recognized on cash flow hedges		(9,407)	(10,136)		(8,872)
Total Interest Expense | Designated as hedge | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items		(45,309)	(51,230)		(36,837)
Discount amortization recognized on hedged items		631	(745)		668
Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives		0	0		0
Losses on financial derivatives | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items		0	0		0
(Losses)/gains on fair value hedging relationships		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
Interest settlements reclassified from AOCI into net income on derivatives		0	0		0
Recognized on hedged items		0	0		0
Expense recognized on cash flow hedges		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
Discount amortization recognized on hedged items		0	0		0
Losses on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives		5,282	(246)		(3,687)
Interest Rate Swap | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives		(10,457)	(52,805)		(6,764)
Income/(expense) related to interest settlements on fair value hedging relationships		88,564	62,183		27,253
Recognized on derivatives	$ (239,514)	(216,218)			(14,413)
Interest Rate Swap | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Total interest expense					(10,920)
(Losses)/gains on financial derivatives		10,321	(4,204)		7,206
Interest expense on interest rate swaps		(4,213)	5,808
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives		(2,177)	(60,056)		1,861
Income/(expense) related to interest settlements on fair value hedging relationships		116,432	66,114		67,099
Recognized on derivatives		(184,478)	(206,281)		(20,279)
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Total interest expense					0
(Losses)/gains on financial derivatives		0	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		(2,053)	(19,135)		(630)
Income/(expense) related to interest settlements on fair value hedging relationships		24,299	21,658		5,654
Recognized on derivatives		(50,141)	(76,565)		5,031
Interest Rate Swap | Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Total interest expense					0
(Losses)/gains on financial derivatives		0	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		(6,227)	26,386		(7,995)
Income/(expense) related to interest settlements on fair value hedging relationships		(52,167)	(25,589)		(45,500)
Recognized on derivatives		18,401	43,332		835
Interest Rate Swap | Total Interest Expense | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Total interest expense					0
(Losses)/gains on financial derivatives		0	0		0
Interest expense on interest rate swaps		0	0
Interest Rate Swap | Losses on financial derivatives | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives		0	0		0
Income/(expense) related to interest settlements on fair value hedging relationships		0	0		0
Recognized on derivatives		0	0		0
Interest Rate Swap | Losses on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
Total interest expense					(10,920)
(Losses)/gains on financial derivatives		10,321	(4,204)		7,206
Interest expense on interest rate swaps		(4,213)	5,808
Treasury futures | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives		(826)	(1,850)		27
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
Treasury futures | Interest Income Loans | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives		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
Treasury futures | Losses on financial derivatives | No hedge designation
Derivative Instruments, Gain (Loss) [Line Items]
(Losses)/gains on financial derivatives		$ (826)	$ (1,850)		$ 27