Condensed Consolidated Statements of Changes in Common Stockholders' Investment (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Statement Of Stockholders Equity [Abstract]
Cash dividends declared, per share	$ 0.65	$ 0.65	$ 2.60	$ 2.60
Other comprehensive income, tax (expense)/benefit	$ (1)	$ 13	$ (4)	$ 22
Purchase of treasury stock			0	20,000.00
Employee incentive plans and other, shares issued	300,000	100,000	3,700,000	600,000