Business Segment Reporting - Core Earnings (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment	7
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	$ 69,402	$ 55,129	$ 131,277	$ 108,380
Guarantee and commitment fees	3,213	2,997	6,908	6,027
Other income/(expense)	3,926	(2,693)	20,612	2,170
Total revenues	76,541	55,433	158,797	116,577
Release of/(provision for) losses	1,372	761	1,316	(152)
Release of reserve for losses	163	222	273	1,166
Operating expenses	(20,048)	(16,878)	(41,436)	(35,759)
Total non-interest expense	(19,885)	(16,656)	(41,163)	(34,593)
Core earnings before income taxes	58,028	39,538	118,950	81,832
Income tax (expense)/benefit	(12,132)	(8,252)	(25,217)	(17,319)
Core earnings before preferred stock dividends	45,896	31,286	93,733	64,513
Preferred stock dividends	(6,792)	(5,842)	(13,583)	(11,111)
Loss on retirement of preferred stock		0
Segment core earnings	39,104	25,444	80,150	53,402
Total Assets	25,916,403	24,181,245	25,916,403	24,181,245	$ 25,145,491
Total on- and off-balance sheet program assets at principal balance	24,479,391	22,197,161	24,479,391	22,197,161
Reconciling Adjustments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	0	0	0	0
Less: reconciling adjustments	8,456	(1,422)	12,492	(2,030)
Net effective spread	8,456	(1,422)	12,492	(2,030)
Guarantee and commitment fees	(1,496)	(1,337)	(2,358)	(2,547)
Other income/(expense)	3,619	(2,994)	19,791	1,418
Total revenues	10,579	(5,753)	29,925	(3,159)
Release of/(provision for) losses	0	0	0	0
Release of reserve for losses	0	0	0	0
Operating expenses	0	0	0	0
Total non-interest expense	0	0	0	0
Core earnings before income taxes	10,579	(5,753)	29,925	(3,159)
Income tax (expense)/benefit	(2,223)	1,211	(6,284)	664
Core earnings before preferred stock dividends	8,356	(4,542)	23,641	(2,495)
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0
Segment core earnings	8,356	(4,542)	23,641	(2,495)
Total Assets	0	0	0	0
Total on- and off-balance sheet program assets at principal balance	0	0	0	0
Farm & Ranch
Segment Reporting Information, Profit (Loss) [Abstract]
Release of/(provision for) losses		600
Farm & Ranch | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	33,670	30,478	65,024	58,124
Less: reconciling adjustments	(1,080)	(1,315)	(2,080)	(2,500)
Net effective spread	32,590	29,163	62,944	55,624
Guarantee and commitment fees	4,338	4,010	8,554	7,918
Other income/(expense)	161	430	561	1,002
Total revenues	37,089	33,603	72,059	64,544
Release of/(provision for) losses	857	575	347	575
Release of reserve for losses	111	181	185	912
Operating expenses	0	0	0	0
Total non-interest expense	111	181	185	912
Core earnings before income taxes	38,057	34,359	72,591	66,031
Income tax (expense)/benefit	(7,991)	(7,216)	(15,243)	(13,866)
Core earnings before preferred stock dividends	30,066	27,143	57,348	52,165
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0
Segment core earnings	30,066	27,143	57,348	52,165
Total Assets	13,686,589	12,327,696	13,686,589	12,327,696
Total on- and off-balance sheet program assets at principal balance	16,591,999	14,873,926	16,591,999	14,873,926
Corporate AgFinance | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	6,929	6,676	14,138	13,597
Less: reconciling adjustments	0	0	0	0
Net effective spread	6,929	6,676	14,138	13,597
Guarantee and commitment fees	43	2	62	10
Other income/(expense)	143	0	257	0
Total revenues	7,115	6,678	14,457	13,607
Release of/(provision for) losses	(650)	97	(1,165)	36
Release of reserve for losses	0	0	0	0
Operating expenses	0	0	0	0
Total non-interest expense	0	0	0	0
Core earnings before income taxes	6,465	6,775	13,292	13,643
Income tax (expense)/benefit	(1,357)	(1,424)	(2,791)	(2,865)
Core earnings before preferred stock dividends	5,108	5,351	10,501	10,778
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0
Segment core earnings	5,108	5,351	10,501	10,778
Total Assets	1,521,102	1,661,734	1,521,102	1,661,734
Total on- and off-balance sheet program assets at principal balance	1,567,311	1,664,059	1,567,311	1,664,059
Rural  Utilities | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	3,772	1,793	6,965	3,547
Less: reconciling adjustments	(39)	(34)	(73)	(67)
Net effective spread	3,733	1,759	6,892	3,480
Guarantee and commitment fees	308	313	620	632
Other income/(expense)	0	1	0	2
Total revenues	4,041	2,073	7,512	4,114
Release of/(provision for) losses	1,172	101	2,341	(532)
Release of reserve for losses	52	41	88	254
Operating expenses	0	0	0	0
Total non-interest expense	52	41	88	254
Core earnings before income taxes	5,265	2,215	9,941	3,836
Income tax (expense)/benefit	(1,105)	(465)	(2,087)	(806)
Core earnings before preferred stock dividends	4,160	1,750	7,854	3,030
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0
Segment core earnings	4,160	1,750	7,854	3,030
Total Assets	5,632,551	5,043,265	5,632,551	5,043,265
Total on- and off-balance sheet program assets at principal balance	6,172,063	5,566,591	6,172,063	5,566,591
Renewable Energy | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	468	378	843	626
Less: reconciling adjustments	0	0	0	0
Net effective spread	468	378	843	626
Guarantee and commitment fees	20	9	30	14
Other income/(expense)	0	0	0	0
Total revenues	488	387	873	640
Release of/(provision for) losses	(8)	(15)	(210)	(210)
Release of reserve for losses	0	0	0	0
Operating expenses	0	0	0	0
Total non-interest expense	0	0	0	0
Core earnings before income taxes	480	372	663	430
Income tax (expense)/benefit	(101)	(78)	(139)	(90)
Core earnings before preferred stock dividends	379	294	524	340
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0
Segment core earnings	379	294	524	340
Total Assets	126,513	85,486	126,513	85,486
Total on- and off-balance sheet program assets at principal balance	148,018	92,585	148,018	92,585
Funding | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	25,845	15,678	45,585	32,246
Less: reconciling adjustments	(7,337)	2,771	(10,339)	4,597
Net effective spread	18,508	18,449	35,246	36,843
Guarantee and commitment fees	0	0	0	0
Other income/(expense)	0	0	0	0
Total revenues	18,508	18,449	35,246	36,843
Release of/(provision for) losses	0	0	0	0
Release of reserve for losses	0	0	0	0
Operating expenses	0	0	0	0
Total non-interest expense	0	0	0	0
Core earnings before income taxes	18,508	18,449	35,246	36,843
Income tax (expense)/benefit	(3,887)	(3,874)	(7,402)	(7,737)
Core earnings before preferred stock dividends	14,621	14,575	27,844	29,106
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0
Segment core earnings	14,621	14,575	27,844	29,106
Total Assets	0	0	0	0
Total on- and off-balance sheet program assets at principal balance	0	0	0	0
Investments | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	(1,282)	126	(1,278)	240
Less: reconciling adjustments	0	0	0	0
Net effective spread	(1,282)	126	(1,278)	240
Guarantee and commitment fees	0	0	0	0
Other income/(expense)	0	0	0	0
Total revenues	(1,282)	126	(1,278)	240
Release of/(provision for) losses	1	3	3	(21)
Release of reserve for losses	0	0	0	0
Operating expenses	0	0	0	0
Total non-interest expense	0	0	0	0
Core earnings before income taxes	(1,281)	129	(1,275)	219
Income tax (expense)/benefit	269	(27)	268	(46)
Core earnings before preferred stock dividends	(1,012)	102	(1,007)	173
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0
Segment core earnings	(1,012)	102	(1,007)	173
Total Assets	4,802,159	5,032,632	4,802,159	5,032,632
Total on- and off-balance sheet program assets at principal balance	0	0	0	0
Corporate | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	0	0	0	0
Less: reconciling adjustments	0	0	0	0
Net effective spread	0	0	0	0
Guarantee and commitment fees	0	0	0	0
Other income/(expense)	3	(130)	3	(252)
Total revenues	3	(130)	3	(252)
Release of/(provision for) losses	0	0	0	0
Release of reserve for losses	0	0	0	0
Operating expenses	(20,048)	(16,878)	(41,436)	(35,759)
Total non-interest expense	(20,048)	(16,878)	(41,436)	(35,759)
Core earnings before income taxes	(20,045)	(17,008)	(41,433)	(36,011)
Income tax (expense)/benefit	4,263	3,621	8,461	7,427
Core earnings before preferred stock dividends	(15,782)	(13,387)	(32,972)	(28,584)
Preferred stock dividends	(6,792)	(5,842)	(13,583)	(11,111)
Loss on retirement of preferred stock		0
Segment core earnings	(22,574)	(19,229)	(46,555)	(39,695)
Total Assets	147,489	30,432	147,489	30,432
Total on- and off-balance sheet program assets at principal balance	$ 0	$ 0	$ 0	$ 0