Short-Term Borrowings - Outstanding (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Aug. 31, 2022	May 31, 2022
Short-term Debt [Line Items]
Short-term borrowings	$ 5,270,826	$ 4,981,167
Commercial paper
Short-term Debt [Line Items]
Short-term borrowings	$ 2,667,027	$ 2,382,882
Commercial paper | Debt | Credit availability concentration risk
Short-term Debt [Line Items]
Concentration risk, percentage	9.00%	9.00%
Commercial paper dealers, net of discounts
Short-term Debt [Line Items]
Short-term borrowings	$ 1,278,986	$ 1,024,813
Commercial paper dealers, net of discounts | Debt | Credit availability concentration risk
Short-term Debt [Line Items]
Concentration risk, percentage	4.00%	4.00%
Commercial paper members, at par
Short-term Debt [Line Items]
Short-term borrowings	$ 1,388,041	$ 1,358,069
Commercial paper members, at par | Debt | Credit availability concentration risk
Short-term Debt [Line Items]
Concentration risk, percentage	5.00%	5.00%
Select notes to members
Short-term Debt [Line Items]
Short-term borrowings	$ 1,712,778	$ 1,753,441
Select notes to members | Debt | Credit availability concentration risk
Short-term Debt [Line Items]
Concentration risk, percentage	6.00%	6.00%
Daily liquidity fund notes to members
Short-term Debt [Line Items]
Short-term borrowings	$ 481,078	$ 427,790
Daily liquidity fund notes to members | Debt | Credit availability concentration risk
Short-term Debt [Line Items]
Concentration risk, percentage	2.00%	1.00%
Medium-term notes to members
Short-term Debt [Line Items]
Short-term borrowings	$ 409,943	$ 417,054
Medium-term notes to members | Debt | Credit availability concentration risk
Short-term Debt [Line Items]
Concentration risk, percentage	1.00%	1.00%
Short-term debt | Debt | Credit availability concentration risk
Short-term Debt [Line Items]
Concentration risk, percentage	18.00%	17.00%