Fair Value of Option Grant Assumptions (Parenthetical) (Detail) (Total Shareholders Return)	3 Months Ended
	Oct. 31, 2013		Oct. 31, 2012
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]

[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%.