Business Segment Reporting - Core Earnings (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	$ 55,005	$ 44,661	$ 163,385	$ 134,321
Less: reconciling adjustments	0	0	0	0
Net effective spread	0	0	0	0
Guarantee and commitment fees	3,155	3,159	9,182	9,495
Other income/(expense)	(1,475)	(228)	695	(388)
Non-interest income/(loss)	1,680	2,931	9,877	9,107
(Provision for)/release of losses	(366)	(653)	(518)	(4,542)
Release of reserve for losses	111	(547)	1,277	(540)
Other non-interest expense	(17,107)	(14,560)	(52,866)	(44,882)
Non-interest expense	(16,996)	(15,107)	(51,589)	(45,422)
Core earnings before income taxes	39,323	31,832	121,155	93,464
Income tax (expense)/benefit	(8,260)	(6,340)	(25,579)	(19,516)
Core earnings before preferred stock dividends	31,063	25,492	95,576	73,948
Preferred stock dividends	(6,774)	(5,166)	(17,885)	(12,536)
Loss on retirement of preferred stock		(1,667)		(1,667)
Segment core earnings	24,289	18,659	77,691	59,745
Total assets at carrying value	24,744,368	23,998,837	24,744,368	23,998,837	$ 24,355,501
Total on- and off-balance sheet program assets at principal balance	23,118,791	21,989,288	23,118,791	21,989,288
Corporate
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	2,938	1,941	8,234	5,025
Less: reconciling adjustments	(50)	431	190	74
Net effective spread	2,888	2,372	8,424	5,099
Guarantee and commitment fees	0	0	0	0
Other income/(expense)	128	(125)	(123)	(413)
Non-interest income/(loss)	128	(125)	(123)	(413)
(Provision for)/release of losses	6	1	(16)	(28)
Release of reserve for losses	0	0	0	0
Other non-interest expense	(4,145)	(3,938)	(13,903)	(12,171)
Non-interest expense	(4,145)	(3,938)	(13,903)	(12,171)
Core earnings before income taxes	(1,123)	(1,690)	(5,618)	(7,513)
Income tax (expense)/benefit	234	701	1,043	1,689
Core earnings before preferred stock dividends	(889)	(989)	(4,575)	(5,824)
Preferred stock dividends	(6,774)	(5,166)	(17,885)	(12,536)
Loss on retirement of preferred stock		0		0
Segment core earnings	(7,663)	(6,155)	(22,460)	(18,360)
Total assets at carrying value	4,693,750	4,576,909	4,693,750	4,576,909
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	(920)	(7,141)	(2,950)	(8,113)
Net effective spread	(920)	(7,141)	(2,950)	(8,113)
Guarantee and commitment fees	(1,167)	(1,500)	(3,714)	(5,003)
Other income/(expense)	(2,162)	(681)	(744)	(3,048)
Non-interest income/(loss)	(3,329)	(2,181)	(4,458)	(8,051)
(Provision for)/release of 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	(4,249)	(9,322)	(7,408)	(16,164)
Income tax (expense)/benefit	892	1,957	1,556	3,395
Core earnings before preferred stock dividends	(3,357)	(7,365)	(5,852)	(12,769)
Preferred stock dividends		0	0	0
Loss on retirement of preferred stock		(1,667)		(1,667)
Segment core earnings	(3,357)	(9,032)	(5,852)	(14,436)
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]
(Provision for)/release of losses	(414)	300	239	412
Release of reserve for losses	91	(628)	994	(262)
Farm & Ranch | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	24,893	18,093	70,805	53,768
Less: reconciling adjustments	(526)	(68)	(1,006)	(4,072)
Net effective spread	24,367	18,025	69,799	49,696
Guarantee and commitment fees	3,831	4,111	11,403	12,822
Other income/(expense)	405	443	1,118	2,197
Non-interest income/(loss)	4,236	4,554	12,521	15,019
(Provision for)/release of losses	(414)	300	239	412
Release of reserve for losses	91	(628)	994	(262)
Other non-interest expense	(6,275)	(5,381)	(18,679)	(16,632)
Non-interest expense	(6,184)	(6,009)	(17,685)	(16,894)
Core earnings before income taxes	22,005	16,870	64,874	48,233
Income tax (expense)/benefit	(4,621)	(3,543)	(13,623)	(10,129)
Core earnings before preferred stock dividends	17,384	13,327	51,251	38,104
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0		0
Segment core earnings	17,384	13,327	51,251	38,104
Total assets at carrying value	6,883,879	5,961,307	6,883,879	5,961,307
Total on- and off-balance sheet program assets at principal balance	9,445,359	8,249,349	9,445,359	8,249,349
USDA Guarantees | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	6,449	4,747	18,227	14,691
Less: reconciling adjustments	398	1,118	1,969	488
Net effective spread	6,847	5,865	20,196	15,179
Guarantee and commitment fees	166	213	522	658
Other income/(expense)	152	135	441	864
Non-interest income/(loss)	318	348	963	1,522
(Provision for)/release of losses	0	0	0	0
Release of reserve for losses	0	0	0	0
Other non-interest expense	(2,284)	(1,643)	(7,080)	(5,045)
Non-interest expense	(2,284)	(1,643)	(7,080)	(5,045)
Core earnings before income taxes	4,881	4,570	14,079	11,656
Income tax (expense)/benefit	(1,025)	(960)	(2,957)	(2,448)
Core earnings before preferred stock dividends	3,856	3,610	11,122	9,208
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0		0
Segment core earnings	3,856	3,610	11,122	9,208
Total assets at carrying value	2,522,382	2,487,687	2,522,382	2,487,687
Total on- and off-balance sheet program assets at principal balance	2,722,702	2,735,128	2,722,702	2,735,128
Rural Utilities
Segment Reporting Information, Profit (Loss) [Abstract]
(Provision for)/release of losses	120	(1,182)	(701)	(4,704)
Release of reserve for losses	20	80	283	(279)
Rural Utilities | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	7,018	5,709	19,995	12,778
Less: reconciling adjustments	(554)	1,230	(242)	4,597
Net effective spread	6,464	6,939	19,753	17,375
Guarantee and commitment fees	320	328	956	995
Other income/(expense)	2	0	3	12
Non-interest income/(loss)	322	328	959	1,007
(Provision for)/release of losses	120	(1,182)	(701)	(4,704)
Release of reserve for losses	20	81	283	(278)
Other non-interest expense	(1,889)	(1,438)	(5,784)	(4,428)
Non-interest expense	(1,869)	(1,357)	(5,501)	(4,706)
Core earnings before income taxes	5,037	4,728	14,510	8,972
Income tax (expense)/benefit	(1,058)	(993)	(3,047)	(1,884)
Core earnings before preferred stock dividends	3,979	3,735	11,463	7,088
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0		0
Segment core earnings	3,979	3,735	11,463	7,088
Total assets at carrying value	2,249,071	2,256,011	2,249,071	2,256,011
Total on- and off-balance sheet program assets at principal balance	2,817,427	2,685,309	2,817,427	2,685,309
Institutional Credit | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	13,707	14,171	46,124	48,059
Less: reconciling adjustments	1,652	4,430	2,039	7,026
Net effective spread	15,359	18,601	48,163	55,085
Guarantee and commitment fees	5	7	15	23
Other income/(expense)	0	0	0	0
Non-interest income/(loss)	5	7	15	23
(Provision for)/release of losses	(78)	228	(40)	(222)
Release of reserve for losses	0	0	0	0
Other non-interest expense	(2,514)	(2,160)	(7,420)	(6,606)
Non-interest expense	(2,514)	(2,160)	(7,420)	(6,606)
Core earnings before income taxes	12,772	16,676	40,718	48,280
Income tax (expense)/benefit	(2,682)	(3,502)	(8,551)	(10,139)
Core earnings before preferred stock dividends	10,090	13,174	32,167	38,141
Preferred stock dividends	0	0	0	0
Loss on retirement of preferred stock		0		0
Segment core earnings	10,090	13,174	32,167	38,141
Total assets at carrying value	8,395,286	8,716,923	8,395,286	8,716,923
Total on- and off-balance sheet program assets at principal balance	$ 8,133,303	$ 8,319,502	$ 8,133,303	$ 8,319,502