Supplemental information - Summary of Dividends per Share (Details) - $ / shares	3 Months Ended						9 Months Ended
	May 31, 2025	Feb. 28, 2025	Nov. 30, 2024	May 31, 2024	Feb. 29, 2024	Nov. 30, 2023	May 31, 2025	May 31, 2024
Supplemental Cash Flow Elements [Abstract]
Cash dividends declared (in dollars per share)	$ 0	$ 0	$ 0.2500	$ 0.2500	$ 0.2500	$ 0.4800	$ 0.2500	$ 0.9800