Interest Income and Interest Expense - Schedule of Interest Income and Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	Feb. 28, 2022	Feb. 28, 2021
Interest income:
Investment securities	$ 3,845	$ 3,907	$ 12,078	$ 11,650
Interest income	285,206	278,172	851,626	834,255
Interest expense:
Short-term borrowings	3,802	3,473	10,271	11,217
Total interest expense	173,654	173,040	522,027	527,438
Net interest income	111,552	105,132	329,599	306,817
Loans receivable
Interest income:
Loans	281,361	274,265	839,548	822,605
Long-term debt
Interest expense:
Long-term debt and subordinated debt	143,639	143,210	432,608	436,702
Subordinated debt
Interest expense:
Long-term debt and subordinated debt	$ 26,213	$ 26,357	$ 79,148	$ 79,519