Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	May 31, 2019	May 31, 2018	May 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (in dollars per share)	$ 0.86	$ 0.78	$ 0.70
Dividends declared per preferred share (in dollars per share)	$ 0.10	$ 0.10	$ 0.10