Consolidated Statements of Changes in Shareholders Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Statement Of Stockholders Equity [Abstract]
Other comprehensive loss, tax	$ 9	$ (67)	$ (44)
Purchase of treasury stock	3,000,000	18,200,000	8,100,000
Cash dividends declared, per share	$ 1.60	$ 1.00	$ 0.80
Employee incentive plans and other, shares issued	3,500,000	2,000,000	3,700,000