Financial Derivatives - Schedule of Net Income/(Expense) Recognized (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income, Operating										$ 290,953	$ 203,796
Interest Income Loans									$ 229,675	198,152	162,150
Total Interest Expense	$ (113,584)	$ (121,384)	$ (122,074)	$ (114,916)	$ (104,237)	$ (97,557)	$ (91,737)	$ (76,317)	(471,958)	(369,848)	(242,885)
Gains/(losses) on financial derivatives									5,282	(3,687)	753
Total									96,895	115,570	123,814
Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									208,311	19,354	(2,413)
(Losses)/gains on fair value hedging relationships									(7,907)	4,941	(719)
Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items									(4)	(6)	(5)
Interest settlements reclassified from AOCI into net income on derivatives									1,166	316	(1,974)
Recognized on hedged items									(10,569)	(9,182)	(4,133)
Expense recognized on cash flow hedges									(9,407)	(8,872)
Expense recognized on cash flow hedges											(6,432)
Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									99,652	34,685	35,485
Discount amortization recognized on hedged items									(631)	(668)	(345)
Losses recognized in income for hedge ineffectiveness											(320)
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									5,282	(3,687)	1,792
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									181,144	21,460	0
(Losses)/gains on fair value hedging relationships									(3,334)	1,181	0
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
Expense recognized on cash flow hedges											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									118,609	65,238	46,389
Discount amortization recognized on hedged items									0	0	0
Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									0	0	0
Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									43,194	(5,243)	0
(Losses)/gains on fair value hedging relationships									(6,947)	(212)	0
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
Expense recognized on cash flow hedges											0
Interest Income Loans | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									26,352	6,284	3,379
Discount amortization recognized on hedged items									0	0	0
Interest Income Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									0	0	0
Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									(16,027)	3,137	0
(Losses)/gains on fair value hedging relationships									2,374	3,972	0
Total Interest Expense | Cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Discount amortization recognized on hedged items									(4)	(6)	(5)
Interest settlements reclassified from AOCI into net income on derivatives									1,166	316	(1,974)
Recognized on hedged items									(10,569)	(9,182)	(4,133)
Expense recognized on cash flow hedges									(9,407)	(8,872)
Expense recognized on cash flow hedges											(6,112)
Total Interest Expense | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									(45,309)	(36,837)	(14,283)
Discount amortization recognized on hedged items									(631)	(668)	(345)
Total Interest Expense | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									0	0	0
Gains/(losses) on financial derivatives | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on hedged items									0	0	(2,413)
(Losses)/gains on fair value hedging relationships									0	0	(719)
Gains/(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
Expense recognized on cash flow hedges											(320)
Gains/(losses) on financial derivatives | Designated as Hedging Instrument | 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 recognized in income for hedge ineffectiveness											(320)
Gains/(losses) on financial derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									5,282	(3,687)	1,792
Interest Rate Swap | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives									(10,457)	(6,764)	(8,845)
Income/(expense) related to interest settlements on fair value hedging relationships									88,564	27,253	26,295
Recognized on derivatives									(216,218)	(14,413)	1,694
Gains attributable to fair value of swaps at inception											(100)
Gains recognized as hedge ineffectiveness											600
Interest Rate Swap | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense									(4,213)	(10,920)	(10,200)
Gains/(losses) on financial derivatives									10,321	7,206	12,240
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)	1,861	(10,346)
Income/(expense) related to interest settlements on fair value hedging relationships									116,432	67,099	36,043
Recognized on derivatives									(184,478)	(20,279)	0
Interest Rate Swap | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Losses recognized in income for hedge ineffectiveness											0
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	0
Gains/(losses) on financial derivatives									0	0	0
Interest Rate Swap | Interest Income Loans | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives									(2,053)	(630)	(1,141)
Income/(expense) related to interest settlements on fair value hedging relationships									24,299	5,654	2,238
Recognized on derivatives									(50,141)	5,031	0
Interest Rate Swap | Interest Income Loans | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Losses recognized in income for hedge ineffectiveness											0
Interest Rate Swap | Interest Income Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense									0	0	0
Gains/(losses) on financial derivatives									0	0	0
Interest Rate Swap | Total Interest Expense | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives									(6,227)	(7,995)	2,642
Income/(expense) related to interest settlements on fair value hedging relationships									(52,167)	(45,500)	(11,986)
Recognized on derivatives									18,401	835	0
Interest Rate Swap | Total Interest Expense | Designated as Hedging Instrument | Fair value hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Losses recognized in income for hedge ineffectiveness											0
Interest Rate Swap | Total Interest Expense | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense									0	0	0
Gains/(losses) on financial derivatives									0	0	0
Interest Rate Swap | Gains/(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	1,694
Interest Rate Swap | Gains/(losses) on financial derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Total Interest Expense									(4,213)	(10,920)	(10,200)
Gains/(losses) on financial derivatives									10,321	7,206	12,240
Treasury futures | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									(826)	27	340
Treasury futures | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									0	0	0
Treasury futures | Interest Income Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									0	0	0
Treasury futures | Total Interest Expense | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									0	0	0
Treasury futures | Gains/(losses) on financial derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives									$ (826)	$ 27	340
Forward Contracts | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives											(588)
Forward Contracts | Interest Income Farmer Mac Guaranteed Securities and USDA Securities | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives											0
Forward Contracts | Interest Income Loans | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives											0
Forward Contracts | Total Interest Expense | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives											0
Forward Contracts | Gains/(losses) on financial derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gains/(losses) on financial derivatives											$ (588)