Condensed Consolidated Statements of Changes in Common Stockholders' Investment (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Statement Of Stockholders Equity [Abstract]
Cash dividends declared, per share	$ 0.65	$ 0.65	$ 2.60	$ 2.60
Other comprehensive income, tax (expense)/benefit	$ 13	$ (2)	$ 22	$ 43
Purchase of treasury stock	0.0	600,000	20,000.00	6,000,000.0
Employee incentive plans and other, shares issued	100,000	100,000	600,000	600,000