Loans - Schedule of non-performing loans (Details) $ in Thousands	12 Months Ended
	May 31, 2023 USD ($) borrower	May 31, 2022 USD ($) borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 32,532,086	$ 30,063,386
% of Total Loans Outstanding	100.00%	100.00%
Non-performing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Borrowers, Nonperforming Loans | borrower	2	3
Outstanding amount	$ 89,334	$ 227,790
% of Total Loans Outstanding	0.27%	0.76%
CFC
Accounts, Notes, Loans and Financing Receivable [Line Items]
% of Total Loans Outstanding	96.00%	96.00%
CFC | Power supply
Accounts, Notes, Loans and Financing Receivable [Line Items]
% of Total Loans Outstanding	17.00%	17.00%
CFC | Non-performing loans | Power supply
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Borrowers, Nonperforming Loans | borrower	2	3
Outstanding amount	$ 89,334	$ 227,790
% of Total Loans Outstanding	0.27%	0.76%