Business Segment Reporting - Core Earnings - Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	$ 41,312	$ 40,599
Less: reconciling adjustments	0	0
Net effective spread	0	0
Guarantee and commitment fees	3,196	3,513
Other income/(expense)	(7,891)	177
Non-interest income/(loss)	(4,695)	3,690
(Provision for)/release of losses	(3,438)	264
Provision for reserve for losses	(393)	129
Other non-interest expense	(16,215)	(12,890)
Non-interest expense	(16,608)	(12,761)
Core earnings before income taxes	16,571	31,792
Income tax (expense)/benefit	(3,741)	(6,622)
Core earnings before preferred stock dividends	12,830	25,170
Preferred stock dividends	(3,431)	(3,296)
Segment core earnings/(losses)	9,399	21,874
Total assets at carrying value	23,180,110	19,797,777	$ 21,709,374
Total on- and off-balance sheet program assets at principal balance	21,539,312	20,506,913
Corporate
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	1,855	2,962
Less: reconciling adjustments	123	(468)
Net effective spread	1,978	2,494
Guarantee and commitment fees	0	0
Other income/(expense)	(129)	22
Non-interest income/(loss)	(129)	22
(Provision for)/release of losses	(14)	0
Provision for reserve for losses	0	0
Other non-interest expense	(4,433)	(3,638)
Non-interest expense	(4,433)	(3,638)
Core earnings before income taxes	(2,598)	(1,122)
Income tax (expense)/benefit	283	290
Core earnings before preferred stock dividends	(2,315)	(832)
Preferred stock dividends	(3,431)	(3,296)
Segment core earnings/(losses)	(5,746)	(4,128)
Total assets at carrying value	4,367,223	2,962,154
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	(2,851)	1,798
Net effective spread	(2,851)	1,798
Guarantee and commitment fees	(1,700)	(1,906)
Other income/(expense)	(9,050)	(332)
Non-interest income/(loss)	(10,750)	(2,238)
(Provision for)/release of losses	0	0
Provision for reserve for losses	0	0
Other non-interest expense	0	0
Non-interest expense	0	0
Core earnings before income taxes	(13,601)	(440)
Income tax (expense)/benefit	2,857	93
Core earnings before preferred stock dividends	(10,744)	(347)
Preferred stock dividends	0	0
Segment core earnings/(losses)	(10,744)	(347)
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]
(Provision for)/release of losses	(808)
Provision for reserve for losses	(4)	129
Farm & Ranch | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	16,365	15,282
Less: reconciling adjustments	(1,427)	(2,545)
Net effective spread	14,938	12,737
Guarantee and commitment fees	4,317	4,744
Other income/(expense)	1,169	480
Non-interest income/(loss)	5,486	5,224
(Provision for)/release of losses	(808)	264
Provision for reserve for losses	(4)	129
Other non-interest expense	(5,997)	(4,799)
Non-interest expense	(6,001)	(4,670)
Core earnings before income taxes	13,615	13,555
Income tax (expense)/benefit	(2,859)	(2,847)
Core earnings before preferred stock dividends	10,756	10,708
Preferred stock dividends	0	0
Segment core earnings/(losses)	10,756	10,708
Total assets at carrying value	5,457,134	4,698,250
Total on- and off-balance sheet program assets at principal balance	7,811,594	7,215,585
USDA Guarantees | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	4,541	4,442
Less: reconciling adjustments	84	(478)
Net effective spread	4,625	3,964
Guarantee and commitment fees	235	224
Other income/(expense)	112	0
Non-interest income/(loss)	347	224
(Provision for)/release of losses	0	0
Provision for reserve for losses	0	0
Other non-interest expense	(1,818)	(1,428)
Non-interest expense	(1,818)	(1,428)
Core earnings before income taxes	3,154	2,760
Income tax (expense)/benefit	(662)	(580)
Core earnings before preferred stock dividends	2,492	2,180
Preferred stock dividends	0	0
Segment core earnings/(losses)	2,492	2,180
Total assets at carrying value	2,341,698	2,191,896
Total on- and off-balance sheet program assets at principal balance	2,646,206	2,484,779
Rural  Utilities
Segment Reporting Information, Profit (Loss) [Abstract]
(Provision for)/release of losses	(2,125)
Provision for reserve for losses	(389)	0
Rural  Utilities | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	4,747	(274)
Less: reconciling adjustments	173	3,507
Net effective spread	4,920	3,233
Guarantee and commitment fees	335	363
Other income/(expense)	7	7
Non-interest income/(loss)	342	370
(Provision for)/release of losses	(2,125)	0
Provision for reserve for losses	(389)	0
Other non-interest expense	(1,604)	(866)
Non-interest expense	(1,993)	(866)
Core earnings before income taxes	1,144	2,737
Income tax (expense)/benefit	(240)	(575)
Core earnings before preferred stock dividends	904	2,162
Preferred stock dividends	0	0
Segment core earnings/(losses)	904	2,162
Total assets at carrying value	1,964,901	1,443,393
Total on- and off-balance sheet program assets at principal balance	2,385,411	2,074,714
Institutional Credit | Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Net interest income	13,804	18,187
Less: reconciling adjustments	3,898	(1,814)
Net effective spread	17,702	16,373
Guarantee and commitment fees	9	88
Other income/(expense)	0	0
Non-interest income/(loss)	9	88
(Provision for)/release of losses	(491)	0
Provision for reserve for losses	0	0
Other non-interest expense	(2,363)	(2,159)
Non-interest expense	(2,363)	(2,159)
Core earnings before income taxes	14,857	14,302
Income tax (expense)/benefit	(3,120)	(3,003)
Core earnings before preferred stock dividends	11,737	11,299
Preferred stock dividends	0	0
Segment core earnings/(losses)	11,737	11,299
Total assets at carrying value	9,049,154	8,502,084
Total on- and off-balance sheet program assets at principal balance	$ 8,696,101	$ 8,731,835