Variable Interest Entities - Schedule of variable interest entities (Details) - USD ($) $ in Thousands	May 31, 2023	May 31, 2022
Variable Interest Entity [Line Items]
Other assets	$ 64,723	$ 23,885
Total assets	34,012,060	31,251,382
Total liabilities	31,422,811	29,109,413
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Loans to members	1,444,662	1,178,479
Other assets	12,612	9,672
Total assets	1,457,274	1,188,151
Total liabilities	$ 19,704	$ 22,958