Organization - Organization (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Product Information [Line Items]
On and Off Balance Sheet Program Assets, At Principal Balance	$ 19,724,524	$ 19,007,311	$ 17,399,475
Farm & Ranch [Member]
Product Information [Line Items]
On and Off Balance Sheet Program Assets, At Principal Balance	7,233,972	6,867,586	6,139,304
USDA Guarantees [Member]
Product Information [Line Items]
On and Off Balance Sheet Program Assets, At Principal Balance	2,515,620	2,352,214	2,094,375
Rural Utilities [Member]
Product Information [Line Items]
On and Off Balance Sheet Program Assets, At Principal Balance	1,592,115	1,882,633	1,878,110
Institutional Credit [Member] [Member]
Product Information [Line Items]
On and Off Balance Sheet Program Assets, At Principal Balance	8,382,817	$ 7,904,878	$ 7,287,686
Notes Payable to Banks [Member]
Product Information [Line Items]
Notes Payable	1,600,000
Medium-term Notes [Member]
Product Information [Line Items]
Notes Payable	$ 14,600,000