Unaudited Condensed Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (in dollars per share)	$ 0.245	$ 0.22	$ 0.465	$ 0.42
Dividends declared per preferred share (in dollars per share)	$ 0	$ 0	$ 0.10	$ 0.10