Supplemental information - Summary of Dividends per Share (Details) - $ / shares	3 Months Ended						9 Months Ended
	May 31, 2023	Feb. 28, 2023	Nov. 30, 2022	May 31, 2022	Feb. 28, 2022	Nov. 30, 2021	May 31, 2023	May 31, 2022
Supplemental Cash Flow Elements [Abstract]
Cash dividends declared (in dollars per share)	$ 0.4800	$ 0.4800	$ 0.4800	$ 0.4775	$ 0.4775	$ 0.4775	$ 1.4400	$ 1.4325