CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	May 31, 2013	Aug. 31, 2012
Statement Of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 349	$ 3,237
Property, plant and equipment, accumulated depreciation	1,768,415	1,578,266
Intangible assets, accumulated amortization	$ 151,980	$ 141,572
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued
Preferred stock, shares outstanding
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	237,218,087	232,069,203
Common stock, shares outstanding	202,651,388	206,028,577
Treasury stock, shares	34,566,699	26,040,626