Financial Derivatives - Schedule of Net Income/(Expense) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income Farmer Mac Guaranteed Securities and USDA Securities	$ 71,517	$ 85,411
Interest Income Loans	60,596	51,397
Total Interest Expense	(108,542)	(114,916)
Losses on financial derivatives	(9,298)	(360)
Total	14,273	21,532
Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	375,223	67,392
(Losses)/gains on fair value hedging relationships	(5,681)	(2,699)
Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	(1)	(1)
Interest settlements reclassified from AOCI into net income on derivatives	(439)	481
Recognized on hedged items	(2,123)	(2,688)
Expense recognized on cash flow hedges	(2,563)	(2,208)
Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	26,227	19,198
Discount amortization recognized on hedged items	(180)	(149)
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	(9,298)	(360)
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	290,379	59,352
(Losses)/gains on fair value hedging relationships	(3,553)	365
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 Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	31,826	24,565
Discount amortization recognized on hedged items	0	0
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	0	0
Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	145,409	16,237
(Losses)/gains on fair value hedging relationships	(497)	(3,845)
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 Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	8,677	4,555
Discount amortization recognized on hedged items	0	0
Interest Income Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	0	0
Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	(60,565)	(8,197)
(Losses)/gains on fair value hedging relationships	(1,631)	781
Total Interest Expense | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items	(1)	(1)
Interest settlements reclassified from AOCI into net income on derivatives	(439)	481
Recognized on hedged items	(2,123)	(2,688)
Expense recognized on cash flow hedges	(2,563)	(2,208)
Total Interest Expense | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	(14,276)	(9,922)
Discount amortization recognized on hedged items	(180)	(149)
Total Interest Expense | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	0	0
Losses 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
Losses 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
Losses on financial derivatives | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items	0	0
Discount amortization recognized on hedged items	0	0
Losses on financial derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	(9,298)	(360)
Interest Rate Swap | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(6,395)	(1,690)
Income/(expense) related to interest settlements on fair value hedging relationships	19,652	17,359
Recognized on derivatives	(380,904)	(70,091)
Interest Rate Swap | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense	(862)	(2,300)
Losses on financial derivatives	(6,550)	2,168
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(6,152)	1,550
Income/(expense) related to interest settlements on fair value hedging relationships	25,674	26,115
Recognized on derivatives	(293,932)	(58,987)
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense	0	0
Losses on financial derivatives	0	0
Interest Rate Swap | Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(1,877)	(22)
Income/(expense) related to interest settlements on fair value hedging relationships	6,800	4,533
Recognized on derivatives	(145,906)	(20,082)
Interest Rate Swap | Interest Income Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense	0	0
Losses on financial derivatives	0	0
Interest Rate Swap | Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	1,634	(3,218)
Income/(expense) related to interest settlements on fair value hedging relationships	(12,822)	(13,289)
Recognized on derivatives	58,934	8,978
Interest Rate Swap | Total Interest Expense | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense	0	0
Losses on financial derivatives	0	0
Interest Rate Swap | Losses 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 | Losses on financial derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense	(862)	(2,300)
Losses on financial derivatives	(6,550)	2,168
Treasury futures | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	(1,886)	(228)
Treasury futures | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	0	0
Treasury futures | Interest Income Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	0	0
Treasury futures | Total Interest Expense | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	0	0
Treasury futures | Losses on financial derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Losses on financial derivatives	$ (1,886)	$ (228)