Condensed Consolidated Statements of Changes in Common Shareholders Investment (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Statement Of Stockholders Equity [Abstract]
Cash dividends declared, per share	$ 0.65	$ 0.50	$ 2.60	$ 2.00
Other comprehensive income, tax (expense)/benefit	$ (2)	$ (2)	$ 43	$ 3
Purchase of treasury stock	600,000	1,200,000	6,000,000	2,400,000
Employee incentive plans and other, shares issued	100,000	700,000	600,000	2,700,000