Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016
Operating Activities:
Net income	$ 1,371	$ 1,415
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	1,507	1,479
Provision for uncollectible accounts	116	76
Stock-based compensation	103	93
Deferred income taxes and other noncash items	327	320
Gain from sale of investment		(35)
Changes in assets and liabilities:
Receivables	(983)	(513)
Other assets	(338)	(250)
Accounts payable and other liabilities	(564)	67
Other, net	(41)	(17)
Cash provided by operating activities	1,498	2,635
Investing Activities:
Capital expenditures	(2,621)	(2,681)
Business acquisitions, net of cash acquired	(44)
Proceeds from asset dispositions and other	12	100
Cash used in investing activities	(2,653)	(2,581)
Financing Activities:
Proceeds from short-term borrowings	250
Principal payments on debt	(28)	(43)
Proceeds from stock issuances	205	164
Dividends paid	(268)	(213)
Purchase of treasury stock	(270)	(334)
Other, net	3	(5)
Cash used in financing activities	(108)	(431)
Effect of exchange rate changes on cash	62	(98)
Net decrease in cash and cash equivalents	(1,201)	(475)
Cash and cash equivalents at beginning of period	3,969	3,534
Cash and cash equivalents at end of period	$ 2,768	$ 3,059