Business Segment Reporting - Core Earnings (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	$ 55,129	$ 48,348	$ 108,380	$ 89,660
Less: reconciling adjustments	0	0	0	0
Net effective spread	0	0	0	0
Guarantee and commitment fees	2,997	3,140	6,027	6,336
Other income/(expense)	(2,693)	7,731	2,170	(160)
Non-interest income/(loss)	304	10,871	8,197	6,176
Release of/(provision for) losses	761	(451)	(152)	(3,889)
Release of reserve for losses	222	400	1,166	7
Other non-interest expense	(16,878)	(14,107)	(35,759)	(30,322)
Non-interest expense	(16,656)	(13,707)	(34,593)	(30,315)
Core earnings before income taxes	39,538	45,061	81,832	61,632
Income tax (expense)/benefit	(8,252)	(9,435)	(17,319)	(13,176)
Core earnings before preferred stock dividends	31,286	35,626	64,513	48,456
Preferred stock dividends	(5,842)	(3,939)	(11,111)	(7,370)
Loss on retirement of preferred stock			0
Segment core earnings	25,444	31,687	53,402	41,086
Total assets at carrying value	24,181,245	23,932,656	24,181,245	23,932,656	$ 24,355,501
Total on- and off-balance sheet program assets at principal balance	22,197,161	22,042,108	22,197,161	22,042,108
Corporate
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	2,761	1,229	5,296	3,084
Less: reconciling adjustments	84	(480)	240	(357)
Net effective spread	2,845	749	5,536	2,727
Guarantee and commitment fees	0	0	0	0
Other income/(expense)	(128)	(159)	(251)	(288)
Non-interest income/(loss)	(128)	(159)	(251)	(288)
Release of/(provision for) losses	3	(15)	(22)	(29)
Release of reserve for losses	0	0	0	0
Other non-interest expense	(4,606)	(3,800)	(9,758)	(8,233)
Non-interest expense	(4,606)	(3,800)	(9,758)	(8,233)
Core earnings before income taxes	(1,886)	(3,225)	(4,495)	(5,823)
Income tax (expense)/benefit	444	705	809	988
Core earnings before preferred stock dividends	(1,442)	(2,520)	(3,686)	(4,835)
Preferred stock dividends	(5,842)	(3,939)	(11,111)	(7,370)
Loss on retirement of preferred stock			0
Segment core earnings	(7,284)	(6,459)	(14,797)	(12,205)
Total assets at carrying value	4,759,010	4,446,504	4,759,010	4,446,504
Total on- and off-balance sheet program assets at principal balance	0	0	0	0
Reconciling Adjustments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	0	0	0	0
Less: reconciling adjustments	(1,422)	1,879	(2,030)	(972)
Net effective spread	(1,422)	1,879	(2,030)	(972)
Guarantee and commitment fees	(1,337)	(1,803)	(2,547)	(3,503)
Other income/(expense)	(2,994)	6,683	1,418	(2,367)
Non-interest income/(loss)	(4,331)	4,880	(1,129)	(5,870)
Release of/(provision for) losses	0	0	0	0
Release of reserve for losses	0	0	0	0
Other non-interest expense	0	0	0	0
Non-interest expense	0	0	0	0
Core earnings before income taxes	(5,753)	6,759	(3,159)	(6,842)
Income tax (expense)/benefit	1,211	(1,419)	664	1,438
Core earnings before preferred stock dividends	(4,542)	5,340	(2,495)	(5,404)
Preferred stock dividends		0	0	0
Loss on retirement of preferred stock			0
Segment core earnings	(4,542)	5,340	(2,495)	(5,404)
Total assets at carrying value	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	626	920	653	112
Release of reserve for losses	172	370	903	366
Farm & Ranch | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	24,057	19,310	45,912	35,675
Less: reconciling adjustments	(79)	(2,577)	(480)	(4,004)
Net effective spread	23,978	16,733	45,432	31,671
Guarantee and commitment fees	3,839	4,394	7,572	8,711
Other income/(expense)	309	585	713	1,754
Non-interest income/(loss)	4,148	4,979	8,285	10,465
Release of/(provision for) losses	626	920	653	112
Release of reserve for losses	172	370	903	366
Other non-interest expense	(5,855)	(5,254)	(12,404)	(11,251)
Non-interest expense	(5,683)	(4,884)	(11,501)	(10,885)
Core earnings before income taxes	23,069	17,748	42,869	31,363
Income tax (expense)/benefit	(4,844)	(3,727)	(9,002)	(6,586)
Core earnings before preferred stock dividends	18,225	14,021	33,867	24,777
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock			0
Segment core earnings	18,225	14,021	33,867	24,777
Total assets at carrying value	6,716,880	5,746,556	6,716,880	5,746,556
Total on- and off-balance sheet program assets at principal balance	9,056,152	8,017,850	9,056,152	8,017,850
USDA Guarantees | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	6,089	5,403	11,778	9,944
Less: reconciling adjustments	893	(714)	1,571	(630)
Net effective spread	6,982	4,689	13,349	9,314
Guarantee and commitment fees	173	210	356	445
Other income/(expense)	120	617	289	729
Non-interest income/(loss)	293	827	645	1,174
Release of/(provision for) losses	0	0	0	0
Release of reserve for losses	0	0	0	0
Other non-interest expense	(2,263)	(1,584)	(4,796)	(3,402)
Non-interest expense	(2,263)	(1,584)	(4,796)	(3,402)
Core earnings before income taxes	5,012	3,932	9,198	7,086
Income tax (expense)/benefit	(1,053)	(826)	(1,932)	(1,488)
Core earnings before preferred stock dividends	3,959	3,106	7,266	5,598
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock			0
Segment core earnings	3,959	3,106	7,266	5,598
Total assets at carrying value	2,506,410	2,408,713	2,506,410	2,408,713
Total on- and off-balance sheet program assets at principal balance	2,726,909	2,677,807	2,726,909	2,677,807
Rural Utilities
Segment Reporting Information, Profit (Loss) [Abstract]
Release of/(provision for) losses	181	(1,397)	(821)	(3,522)
Release of reserve for losses	50	30	263	(359)
Rural Utilities | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	5,328	2,322	12,977	7,069
Less: reconciling adjustments	1,287	3,194	312	3,367
Net effective spread	6,615	5,516	13,289	10,436
Guarantee and commitment fees	317	332	636	667
Other income/(expense)	0	5	1	12
Non-interest income/(loss)	317	337	637	679
Release of/(provision for) losses	181	(1,397)	(821)	(3,522)
Release of reserve for losses	50	30	263	(359)
Other non-interest expense	(1,838)	(1,386)	(3,895)	(2,990)
Non-interest expense	(1,788)	(1,356)	(3,632)	(3,349)
Core earnings before income taxes	5,325	3,100	9,473	4,244
Income tax (expense)/benefit	(1,118)	(651)	(1,989)	(891)
Core earnings before preferred stock dividends	4,207	2,449	7,484	3,353
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock			0
Segment core earnings	4,207	2,449	7,484	3,353
Total assets at carrying value	2,272,425	2,281,490	2,272,425	2,281,490
Total on- and off-balance sheet program assets at principal balance	2,780,027	2,691,621	2,780,027	2,691,621
Institutional Credit | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	16,894	20,084	32,417	33,888
Less: reconciling adjustments	(763)	(1,302)	387	2,596
Net effective spread	16,131	18,782	32,804	36,484
Guarantee and commitment fees	5	7	10	16
Other income/(expense)	0	0	0	0
Non-interest income/(loss)	5	7	10	16
Release of/(provision for) losses	(49)	41	38	(450)
Release of reserve for losses	0	0	0	0
Other non-interest expense	(2,316)	(2,083)	(4,906)	(4,446)
Non-interest expense	(2,316)	(2,083)	(4,906)	(4,446)
Core earnings before income taxes	13,771	16,747	27,946	31,604
Income tax (expense)/benefit	(2,892)	(3,517)	(5,869)	(6,637)
Core earnings before preferred stock dividends	10,879	13,230	22,077	24,967
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock			0
Segment core earnings	10,879	13,230	22,077	24,967
Total assets at carrying value	7,926,520	9,049,393	7,926,520	9,049,393
Total on- and off-balance sheet program assets at principal balance	$ 7,634,073	$ 8,654,830	$ 7,634,073	$ 8,654,830