BUSINESS SEGMENT REPORTING - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Interest income	$ 415,341			$ 407,728			$ 1,195,777	$ 1,207,751
Interest expense	(316,864)			(320,937)			(909,564)	(947,252)
Less: reconciling adjustments	(708)			(1,395)			(4,561)	(8,463)
Net effective spread	97,769			85,396			281,652	252,036
Guarantee and commitment fees	6,132			4,997			17,494	15,235
Other income/(expense)	1,183			1,225			3,107	2,660
(Provision for)/release of losses	(7,433)			(3,258)			(16,828)	(7,618)
Operating expenses	(17,457)			(14,165)			(50,970)	(42,301)
Income tax (expense)/benefit	(16,841)			(15,581)			(49,235)	(46,205)
Segment core earnings	63,353			58,614			185,220	173,807
Reconciliation to net income:
Net effects of derivatives and trading securities	(1,193)			(1,263)			(1,468)	3,869
Unallocated (expenses)/income	(12,311)			(10,683)			(37,741)	(34,168)
Income tax effect related to reconciling items	5,154			3,160			13,480	7,171
Net income	55,003	$ 54,837	$ 49,651	49,828	$ 47,105	$ 53,746	159,491	150,679
Total on- and off-balance sheet segment assets at principal balance	31,119,162			28,468,303			31,119,162	28,468,303
Off-balance sheet assets under management	(5,264,616)			(4,562,819)			(5,264,616)	(4,562,819)
Unallocated assets	7,525,014			6,709,737			7,525,014	6,709,737
Total Assets	33,379,560			30,615,221			33,379,560	30,615,221	$ 31,324,742
Operating Segments | Farm & Ranch
Segment Reporting Information [Line Items]
Interest income	154,020			155,634			455,919	465,155
Interest expense	(118,081)			(118,818)			(348,394)	(358,928)
Net effective spread	34,840			35,755			104,435	102,754
Guarantee and commitment fees	4,572			4,304			13,674	13,400
Other income/(expense)	1,080			1,176			2,615	2,688
(Provision for)/release of losses	(4,050)			10			(8,351)	(734)
Operating expenses	(6,721)			(6,180)			(20,336)	(18,175)
Income tax (expense)/benefit	(6,240)			(7,364)			(19,323)	(20,987)
Segment core earnings	23,481			27,701			72,714	78,946
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	18,218,755			18,090,374			18,218,755	18,090,374
Operating Segments | Corporate AgFinance
Segment Reporting Information [Line Items]
Interest income	26,662			24,834			77,268	75,758
Interest expense	(17,615)			(18,437)			(50,972)	(53,524)
Net effective spread	9,047			6,397			26,296	22,234
Guarantee and commitment fees	218			168			639	382
Other income/(expense)	111			39			456	(1,101)
(Provision for)/release of losses	(2,787)			(1,779)			(4,229)	(6,755)
Operating expenses	(3,131)			(1,893)			(7,642)	(5,648)
Income tax (expense)/benefit	(727)			(616)			(3,262)	(1,914)
Segment core earnings	2,731			2,316			12,258	7,198
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	1,891,228			1,842,780			1,891,228	1,842,780
Operating Segments | Power & Utilities
Segment Reporting Information [Line Items]
Interest income	69,746			64,345			202,188	198,026
Interest expense	(63,810)			(59,531)			(185,234)	(183,010)
Net effective spread	5,910			4,785			16,875	14,928
Guarantee and commitment fees	212			232			648	733
Other income/(expense)	(7)			0			(7)	0
(Provision for)/release of losses	424			(196)			274	94
Operating expenses	(1,122)			(1,009)			(3,401)	(3,156)
Income tax (expense)/benefit	(1,137)			(801)			(3,020)	(2,647)
Segment core earnings	4,280			3,011			11,369	9,952
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	7,426,517			6,794,435			7,426,517	6,794,435
Operating Segments | Broadband Infrastructure
Segment Reporting Information [Line Items]
Interest income	13,375			9,955			36,367	27,378
Interest expense	(8,996)			(7,161)			(24,490)	(19,849)
Net effective spread	4,379			2,794			11,877	7,529
Guarantee and commitment fees	701			106			1,601	255
Other income/(expense)	0			0			0	0
(Provision for)/release of losses	(410)			(955)			(847)	2,252
Operating expenses	(1,362)			(887)			(3,688)	(2,607)
Income tax (expense)/benefit	(695)			(222)			(1,879)	(1,560)
Segment core earnings	2,613			836			7,064	5,869
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	1,299,097			645,706			1,299,097	645,706
Operating Segments | Renewable Energy
Segment Reporting Information [Line Items]
Interest income	28,616			15,679			72,425	35,428
Interest expense	(20,886)			(11,869)			(53,356)	(26,570)
Net effective spread	7,730			3,810			19,069	8,858
Guarantee and commitment fees	429			187			932	465
Other income/(expense)	0			0			8	0
(Provision for)/release of losses	(616)			(337)			(3,680)	(2,476)
Operating expenses	(1,649)			(1,204)			(4,917)	(3,458)
Income tax (expense)/benefit	(1,238)			(515)			(2,397)	(711)
Segment core earnings	4,656			1,941			9,015	2,678
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	2,283,565			1,095,008			2,283,565	1,095,008
Operating Segments | Funding
Segment Reporting Information [Line Items]
Interest income	36,139			58,095			104,736	175,179
Interest expense	(1,686)			(26,878)			(5,066)	(76,623)
Net effective spread	34,777			30,912			98,049	93,654
Guarantee and commitment fees	0			0			0	0
Other income/(expense)	0			0			0	0
(Provision for)/release of losses	0			0			0	0
Operating expenses	(2,712)			(2,354)			(8,515)	(7,236)
Income tax (expense)/benefit	(6,734)			(5,997)			(18,803)	(18,148)
Segment core earnings	25,331			22,561			70,731	68,270
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	0			0			0	0
Operating Segments | Investments
Segment Reporting Information [Line Items]
Interest income	86,783			79,186			246,874	230,827
Interest expense	(85,790)			(78,243)			(242,052)	(228,748)
Net effective spread	1,086			943			5,051	2,079
Guarantee and commitment fees	0			0			0	0
Other income/(expense)	(1)			10			35	1,073
(Provision for)/release of losses	6			(1)			5	1
Operating expenses	(760)			(638)			(2,471)	(2,021)
Income tax (expense)/benefit	(70)			(66)			(551)	(238)
Segment core earnings	261			248			2,069	894
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	0			0			0	0
Reconciling Adjustments | Farm & Ranch
Segment Reporting Information [Line Items]
Less: reconciling adjustments	(1,099)			(1,061)			(3,090)	(3,473)
Reconciling Adjustments | Corporate AgFinance
Segment Reporting Information [Line Items]
Less: reconciling adjustments	0			0			0	0
Reconciling Adjustments | Power & Utilities
Segment Reporting Information [Line Items]
Less: reconciling adjustments	(26)			(29)			(79)	(88)
Reconciling Adjustments | Broadband Infrastructure
Segment Reporting Information [Line Items]
Less: reconciling adjustments	0			0			0	0
Reconciling Adjustments | Renewable Energy
Segment Reporting Information [Line Items]
Less: reconciling adjustments	0			0			0	0
Reconciling Adjustments | Funding
Segment Reporting Information [Line Items]
Less: reconciling adjustments	324			(305)			(1,621)	(4,902)
Reconciling Adjustments | Investments
Segment Reporting Information [Line Items]
Less: reconciling adjustments	$ 93			$ 0			$ 229	$ 0