BUSINESS SEGMENT REPORTING - Schedule of Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2026	Jun. 30, 2026	Mar. 31, 2026	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Segment Reporting [Line Items]
Interest income	$ 472,492			$ 415,341			$ 1,338,713	$ 1,195,777
Interest (expense)/benefit	(356,568)			(316,864)			(1,003,318)	(909,564)
Less: reconciling adjustments	(2,038)			(708)			(2,072)	(4,561)
Net effective spread	113,886			97,769			333,323	281,652
Guarantee and commitment fees	6,998			6,132			20,757	17,494
Other income/(expense)	1,464			1,183			3,179	3,107
(Provision for)/release of losses	(11,069)			(7,433)			(23,265)	(16,828)
Operating expenses	(19,331)			(17,457)			(58,898)	(50,970)
Income tax (expense)/benefit	(19,309)			(16,841)			(57,571)	(49,235)
Segment core earnings	72,639			63,353			217,525	185,220
Reconciliation to net income:
Net effects of derivatives and trading securities	2,879			(1,193)			3,065	(1,468)
Unallocated (expenses)/income	(15,272)			(12,311)			(45,335)	(37,741)
Income tax effect related to reconciling items	3,965			5,154			15,030	13,480
Net income	64,211	$ 66,951	$ 59,123	55,003	$ 54,837	$ 49,651	190,285	159,491
Total on- and off-balance sheet segment assets at principal balance	38,475,738			31,119,162			38,475,738	31,119,162
Off-balance sheet assets under management	(6,525,042)			(5,264,616)			(6,525,042)	(5,264,616)
Unallocated assets	8,070,690			7,525,014			8,070,690	7,525,014
Total Assets	40,021,386			33,379,560			40,021,386	33,379,560	$ 35,370,157
Operating Segments | Farm & Ranch
Segment Reporting [Line Items]
Interest income	198,694			154,020			554,055	455,919
Interest (expense)/benefit	(158,086)			(118,081)			(433,763)	(348,394)
Net effective spread	39,830			34,840			117,566	104,435
Guarantee and commitment fees	4,782			4,572			14,702	13,674
Other income/(expense)	1,520			1,080			3,323	2,615
(Provision for)/release of losses	(430)			(4,050)			(6,622)	(8,351)
Operating expenses	(7,838)			(6,721)			(25,289)	(20,336)
Income tax (expense)/benefit	(7,951)			(6,240)			(21,572)	(19,323)
Segment core earnings	29,913			23,481			82,108	72,714
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	22,285,578			18,218,755			22,285,578	18,218,755
Operating Segments | Corporate AgFinance
Segment Reporting [Line Items]
Interest income	28,469			26,662			86,982	77,268
Interest (expense)/benefit	(17,541)			(17,615)			(50,346)	(50,972)
Net effective spread	10,928			9,047			36,636	26,296
Guarantee and commitment fees	252			218			762	639
Other income/(expense)	44			111			59	456
(Provision for)/release of losses	(1,385)			(2,787)			(3,929)	(4,229)
Operating expenses	(2,487)			(3,131)			(7,323)	(7,642)
Income tax (expense)/benefit	(1,544)			(727)			(5,503)	(3,262)
Segment core earnings	5,808			2,731			20,702	12,258
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	2,143,737			1,891,228			2,143,737	1,891,228
Operating Segments | Power & Utilities
Segment Reporting [Line Items]
Interest income	79,943			69,746			230,169	202,188
Interest (expense)/benefit	(73,053)			(63,810)			(209,760)	(185,234)
Net effective spread	6,865			5,910			20,318	16,875
Guarantee and commitment fees	195			212			591	648
Other income/(expense)	0			(7)			0	(7)
(Provision for)/release of losses	(219)			424			(526)	274
Operating expenses	(1,228)			(1,122)			(3,583)	(3,401)
Income tax (expense)/benefit	(1,179)			(1,137)			(3,529)	(3,020)
Segment core earnings	4,434			4,280			13,271	11,369
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	8,431,244			7,426,517			8,431,244	7,426,517
Operating Segments | Broadband Infrastructure
Segment Reporting [Line Items]
Interest income	19,735			13,375			53,865	36,367
Interest (expense)/benefit	(12,588)			(8,996)			(34,312)	(24,490)
Net effective spread	7,147			4,379			19,553	11,877
Guarantee and commitment fees	1,088			701			3,044	1,601
Other income/(expense)	0			0			(81)	0
(Provision for)/release of losses	(7,027)			(410)			(8,967)	(847)
Operating expenses	(1,813)			(1,362)			(5,399)	(3,688)
Income tax (expense)/benefit	128			(695)			(1,710)	(1,879)
Segment core earnings	(477)			2,613			6,440	7,064
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	2,020,729			1,299,097			2,020,729	1,299,097
Operating Segments | Renewable Energy
Segment Reporting [Line Items]
Interest income	39,124			28,616			106,976	72,425
Interest (expense)/benefit	(28,010)			(20,886)			(76,010)	(53,356)
Net effective spread	11,114			7,730			30,966	19,069
Guarantee and commitment fees	681			429			1,658	932
Other income/(expense)	(100)			0			(122)	8
(Provision for)/release of losses	(2,008)			(616)			(3,221)	(3,680)
Operating expenses	(2,084)			(1,649)			(6,195)	(4,917)
Income tax (expense)/benefit	(1,597)			(1,238)			(4,848)	(2,397)
Segment core earnings	6,006			4,656			18,238	9,015
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	3,594,450			2,283,565			3,594,450	2,283,565
Operating Segments | Funding
Segment Reporting [Line Items]
Interest income	20,481			36,139			57,652	104,736
Interest (expense)/benefit	17,807			(1,686)			46,774	(5,066)
Net effective spread	37,053			34,777			104,929	98,049
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	(2,888)			(2,712)			(8,279)	(8,515)
Income tax (expense)/benefit	(7,175)			(6,734)			(20,298)	(18,803)
Segment core earnings	26,990			25,331			76,352	70,731
Reconciliation to net income:
Total on- and off-balance sheet segment assets at principal balance	0			0			0	0
Operating Segments | Investments
Segment Reporting [Line Items]
Interest income	86,046			86,783			249,014	246,874
Interest (expense)/benefit	(85,097)			(85,790)			(245,901)	(242,052)
Net effective spread	949			1,086			3,355	5,051
Guarantee and commitment fees	0			0			0	0
Other income/(expense)	0			(1)			0	35
(Provision for)/release of losses	0			6			0	5
Operating expenses	(993)			(760)			(2,830)	(2,471)
Income tax (expense)/benefit	9			(70)			(111)	(551)
Segment core earnings	(35)			261			414	2,069
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 [Line Items]
Less: reconciling adjustments	(778)			(1,099)			(2,726)	(3,090)
Reconciling Adjustments | Corporate AgFinance
Segment Reporting [Line Items]
Less: reconciling adjustments	0			0			0	0
Reconciling Adjustments | Power & Utilities
Segment Reporting [Line Items]
Less: reconciling adjustments	(25)			(26)			(91)	(79)
Reconciling Adjustments | Broadband Infrastructure
Segment Reporting [Line Items]
Less: reconciling adjustments	0			0			0	0
Reconciling Adjustments | Renewable Energy
Segment Reporting [Line Items]
Less: reconciling adjustments	0			0			0	0
Reconciling Adjustments | Funding
Segment Reporting [Line Items]
Less: reconciling adjustments	(1,235)			324			503	(1,621)
Reconciling Adjustments | Investments
Segment Reporting [Line Items]
Less: reconciling adjustments	$ 0			$ 93			$ 242	$ 229