Business Segment Reporting - Core Earnings (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	$ 53,251	$ 41,312
Less: reconciling adjustments	0	0
Net effective spread	0	0
Guarantee and commitment fees	3,030	3,196
Other income/(expense)	4,863	(7,891)
Non-interest income/(loss)	7,893	(4,695)
Release of/(provision for) losses	(913)	(3,438)
Release of reserve for losses	944	(393)
Other non-interest expense	(18,881)	(16,215)
Non-interest expense	(17,937)	(16,608)
Core earnings before income taxes	42,294	16,571
Income tax (expense)/benefit	(9,067)	(3,741)
Core earnings before preferred stock dividends	33,227	12,830
Preferred stock dividends	(5,269)	(3,431)
Segment core earnings	27,958	9,399
Total assets at carrying value	24,013,911	23,180,110	$ 24,013,911	$ 24,355,501
Total on- and off-balance sheet program assets at principal balance		21,539,312	$ 21,862,531
Corporate
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	2,535	1,855
Less: reconciling adjustments	156	123
Net effective spread	2,691	1,978
Guarantee and commitment fees	0	0
Other income/(expense)	(123)	(129)
Non-interest income/(loss)	(123)	(129)
Release of/(provision for) losses	(25)	(14)
Release of reserve for losses	0	0
Other non-interest expense	(5,152)	(4,433)
Non-interest expense	(5,152)	(4,433)
Core earnings before income taxes	(2,609)	(2,598)
Income tax (expense)/benefit	365	283
Core earnings before preferred stock dividends	(2,244)	(2,315)
Preferred stock dividends	(5,269)	(3,431)
Segment core earnings	(7,513)	(5,746)
Total assets at carrying value	4,923,589	4,367,223
Total on- and off-balance sheet program assets at principal balance	0	0
Reconciling Adjustments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	0	0
Less: reconciling adjustments	(608)	(2,851)
Net effective spread	(608)	(2,851)
Guarantee and commitment fees	(1,210)	(1,700)
Other income/(expense)	4,412	(9,050)
Non-interest income/(loss)	3,202	(10,750)
Release of/(provision for) losses	0	0
Release of reserve for losses	0	0
Other non-interest expense	0	0
Non-interest expense	0	0
Core earnings before income taxes	2,594	(13,601)
Income tax (expense)/benefit	(547)	2,857
Core earnings before preferred stock dividends	2,047	(10,744)
Preferred stock dividends	0	0
Segment core earnings	2,047	(10,744)
Total assets at carrying value	0	0
Total on- and off-balance sheet program assets at principal balance	0	0
Farm & Ranch
Segment Reporting Information, Profit (Loss) [Abstract]
Release of/(provision for) losses	27	(808)
Release of reserve for losses	731	(4)
Farm & Ranch | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	21,855	16,365
Less: reconciling adjustments	(401)	(1,427)
Net effective spread	21,454	14,938
Guarantee and commitment fees	3,733	4,317
Other income/(expense)	404	1,169
Non-interest income/(loss)	4,137	5,486
Release of/(provision for) losses	27	(808)
Release of reserve for losses	731	(4)
Other non-interest expense	(6,549)	(5,997)
Non-interest expense	(5,818)	(6,001)
Core earnings before income taxes	19,800	13,615
Income tax (expense)/benefit	(4,158)	(2,859)
Core earnings before preferred stock dividends	15,642	10,756
Preferred stock dividends	0	0
Segment core earnings	15,642	10,756
Total assets at carrying value	6,395,438	5,457,134
Total on- and off-balance sheet program assets at principal balance	8,629,352	7,811,594
USDA Guarantees | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	5,689	4,541
Less: reconciling adjustments	678	84
Net effective spread	6,367	4,625
Guarantee and commitment fees	183	235
Other income/(expense)	169	112
Non-interest income/(loss)	352	347
Release of/(provision for) losses	0	0
Release of reserve for losses	0	0
Other non-interest expense	(2,533)	(1,818)
Non-interest expense	(2,533)	(1,818)
Core earnings before income taxes	4,186	3,154
Income tax (expense)/benefit	(879)	(662)
Core earnings before preferred stock dividends	3,307	2,492
Preferred stock dividends	0	0
Segment core earnings	3,307	2,492
Total assets at carrying value	2,557,412	2,341,698
Total on- and off-balance sheet program assets at principal balance	2,787,065	2,646,206
Rural Utilities
Segment Reporting Information, Profit (Loss) [Abstract]
Release of/(provision for) losses	(1,002)	(2,125)
Release of reserve for losses	213	(389)
Rural Utilities | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	7,649	4,747
Less: reconciling adjustments	(975)	173
Net effective spread	6,674	4,920
Guarantee and commitment fees	319	335
Other income/(expense)	1	7
Non-interest income/(loss)	320	342
Release of/(provision for) losses	(1,002)	(2,125)
Release of reserve for losses	213	(389)
Other non-interest expense	(2,057)	(1,604)
Non-interest expense	(1,844)	(1,993)
Core earnings before income taxes	4,148	1,144
Income tax (expense)/benefit	(871)	(240)
Core earnings before preferred stock dividends	3,277	904
Preferred stock dividends	0	0
Segment core earnings	3,277	904
Total assets at carrying value	2,207,810	1,964,901
Total on- and off-balance sheet program assets at principal balance	2,804,437	2,385,411
Institutional Credit | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	15,523	13,804
Less: reconciling adjustments	1,150	3,898
Net effective spread	16,673	17,702
Guarantee and commitment fees	5	9
Other income/(expense)	0	0
Non-interest income/(loss)	5	9
Release of/(provision for) losses	87	(491)
Release of reserve for losses	0	0
Other non-interest expense	(2,590)	(2,363)
Non-interest expense	(2,590)	(2,363)
Core earnings before income taxes	14,175	14,857
Income tax (expense)/benefit	(2,977)	(3,120)
Core earnings before preferred stock dividends	11,198	11,737
Preferred stock dividends	0	0
Segment core earnings	11,198	11,737
Total assets at carrying value	7,929,662	9,049,154
Total on- and off-balance sheet program assets at principal balance	$ 7,641,677	$ 8,696,101