Condensed Consolidated Statements of Changes in Common Stockholders' Investment (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2020	Aug. 31, 2019
Statement Of Stockholders Equity [Abstract]
Cash dividends declared, per share	$ 1.30	$ 1.30
Other comprehensive income, tax (expense)/benefit	$ 3	$ 9
Purchase of treasury stock	0.0	20,000.00
Employee incentive plans and other, shares issued	1,000,000.0	300,000