CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	May 31, 2018	Aug. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 11,084	$ 14,134
Property, plant and equipment, accumulated depreciation	3,547,148	3,125,390
Intangible assets, accumulated amortization	$ 298,925	$ 269,212
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	256,590,528	253,266,684
Common stock, shares outstanding	168,799,744	177,727,653
Treasury stock, shares	87,790,784	75,539,031