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Equity method investments (Details)	0 Months Ended
	Nov. 30, 2010	Aug. 31, 2013	Aug. 31, 2012	Nov. 30, 2011	Nov. 30, 2010
ECTE [Member]
Schedule of Equity Method Investments [Line Items]
Percentage ownership interest in equity method investment sold					59.96%
Number of years over which remaining ownership interest in equity method investment will be sold	4 years
Portion of remaining interest sold		25.00%	25.00%	25.00%
ENTE [Member]
Schedule of Equity Method Investments [Line Items]
Percentage ownership interest in equity method investment sold	100.00%				100.00%
ERTE [Member]
Schedule of Equity Method Investments [Line Items]
Percentage ownership interest in equity method investment sold	100.00%				100.00%

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- Definition

Number of years over which remaining ownership interest in equity method investment will be sold.

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Percentage ownership interest in equity method investment sold.

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Amount of remaining ownership interest sold.

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