Condensed Consolidated Statements of Changes in Common Stockholders' Investment (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Statement Of Stockholders Equity [Abstract]
Cash dividends declared, per share	$ 0.65	$ 0.65	$ 1.95	$ 1.95
Other comprehensive income, tax (expense)/benefit	$ (1)	$ 14	$ 8	$ 45
Purchase of treasury stock	0.0	2,800,000	20,000.00	5,400,000
Employee incentive plans and other, shares issued	200,000	200,000	500,000	500,000