Property, Plant and Equipment (Details) (USD $)	3 Months Ended		6 Months Ended		14 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Aug. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 4,404,578,000		$ 4,404,578,000		$ 4,404,578,000	$ 4,031,023,000
Depreciation	72,700,000	60,700,000	143,200,000	120,100,000
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Additions			358,700,000
Spiritwood [Member]
Property, Plant and Equipment [Line Items]
Total construction cost, estimate			3,000,000,000
Spiritwood [Member] | Asset under Construction [Member]
Property, Plant and Equipment [Line Items]
Acquisition of property, plant and equipment					$ 68,400,000