Fair Value of Option Grant Assumptions (Parenthetical) (Detail) (Total Shareholders Return)	12 Months Ended
	Jul. 31, 2013		Jul. 31, 2012		Jul. 31, 2011
Total Shareholders Return
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Expected annual dividend yield	0.00%	[1]	0.00%	[1]	0.00%	[1]

[1] Dividends are considered reinvested when calculating TSR. For the purpose of the fair value model, the dividend yield is therefore considered to be 0%.