Interest Income and Interest Expense - Schedule of Interest Income and Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 28, 2026	Feb. 28, 2025	Feb. 28, 2026	Feb. 28, 2025
Interest income:
Cash and investment securities	$ 1,334	$ 2,644	$ 4,638	$ 9,916
Total interest income	449,570	428,860	1,342,690	1,266,856
Interest expense:
Short-term borrowings	46,188	48,996	142,490	145,643
Total interest expense	370,010	361,918	1,120,145	1,072,821
Net interest income	79,560	66,942	222,545	194,035
Long-term debt
Interest expense:
Long-term debt and subordinated debt	294,240	278,359	878,782	822,750
Subordinated debt
Interest expense:
Long-term debt and subordinated debt	29,582	34,563	98,873	104,428
Loans
Interest income:
Loans	$ 448,236	$ 426,216	$ 1,338,052	$ 1,256,940