Long-Term Debt - Long-term debt outstanding (Details) - USD ($) $ in Thousands	May 31, 2026	May 31, 2025
Debt Instrument [Line Items]
Total	$ 28,345,934	$ 27,163,701
Weighted- Average Interest Rate	3.99%	3.99%
Collateral trust bonds
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,670,191	$ 7,082,711
Unamortized discount	(140,322)	(155,393)
Debt issuance costs	(27,466)	(31,616)
Total	$ 6,502,403	$ 6,895,702
Weighted- Average Interest Rate	3.70%	3.68%
Guaranteed Underwriter Program notes payable
Debt Instrument [Line Items]
Long-term debt, gross	$ 5,338,722	$ 6,456,852
Weighted- Average Interest Rate	3.38%	3.31%
Farmer Mac notes payable
Debt Instrument [Line Items]
Long-term debt, gross		$ 3,780,461
Total	$ 3,911,993
Weighted- Average Interest Rate	3.86%	4.00%
Total secured notes payable
Debt Instrument [Line Items]
Total	$ 9,250,715	$ 10,237,313
Total secured long-term debt
Debt Instrument [Line Items]
Total	$ 15,753,118	$ 17,133,015
Weighted- Average Interest Rate	3.63%	3.61%
Medium-term notes sold through dealers(3)
Debt Instrument [Line Items]
Long-term debt, gross	$ 12,242,476	$ 9,637,577
Weighted- Average Interest Rate	4.44%	4.64%
Medium-term notes sold to members
Debt Instrument [Line Items]
Long-term debt, gross	$ 376,726	$ 419,648
Weighted- Average Interest Rate	4.31%	4.61%
Total unsecured medium-term notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 12,619,202	$ 10,057,225
Debt issuance costs	(26,937)	(29,180)
Unamortized premium (discount), net	$ 551	$ 2,641
Weighted- Average Interest Rate	4.44%	4.64%
Total unsecured long-term debt
Debt Instrument [Line Items]
Total	$ 12,592,816	$ 10,030,686
Weighted- Average Interest Rate	4.44%	4.64%