Short-Term Borrowings - Outstanding (Details) - USD ($) $ in Thousands	May 31, 2026	May 31, 2025
Short-term Debt [Line Items]
Amount	$ 5,159,771	$ 5,091,416
Weighted Average Interest Rate	6.19%	6.36%
Total commercial paper
Short-term Debt [Line Items]
Amount	$ 3,221,103	$ 2,992,059
Weighted Average Interest Rate	3.69%	4.34%
Commercial paper sold through dealers, net of discounts
Short-term Debt [Line Items]
Amount	$ 2,338,411	$ 2,206,451
Weighted Average Interest Rate	3.85%	4.47%
Commercial paper sold directly to members, at par
Short-term Debt [Line Items]
Amount	$ 882,692	$ 785,608
Weighted Average Interest Rate	3.27%	3.98%
Select notes to members
Short-term Debt [Line Items]
Amount	$ 1,361,207	$ 1,304,240
Weighted Average Interest Rate	3.54%	4.22%
Daily liquidity fund notes to members
Short-term Debt [Line Items]
Amount	$ 253,271	$ 343,916
Weighted Average Interest Rate	3.00%	3.75%
Medium-term notes sold to members
Short-term Debt [Line Items]
Amount	$ 324,190	$ 451,201
Weighted Average Interest Rate	3.81%	4.62%
Short-term borrowings
Short-term Debt [Line Items]
Weighted Average Interest Rate	3.62%	4.30%