Interest Income and Interest Expense - Schedule of interest income and expense (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2023	May 31, 2022	May 31, 2021
Interest income:
Investment securities	$ 21,585	$ 15,951	$ 15,096
Interest income	1,351,729	1,141,243	1,116,601
Interest expense
Short-term borrowings	165,961	18,265	14,730
Total interest expense	1,036,508	705,534	702,063
Net interest income	315,221	435,709	414,538
Loans
Interest income:
Loans	1,330,144	1,125,292	1,101,505
Long-term debt
Interest expense
Debt	763,700	581,748	581,292
Subordinated debt
Interest expense
Debt	$ 106,847	$ 105,521	$ 106,041