Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (in dollars per share)	$ 0.22	$ 0.20	$ 0.64	$ 0.58
Dividends declared per preferred share (in dollars per share)	$ 0.00	$ 0.00	$ 0.10	$ 0.10