Provision for Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended
	Oct. 31, 2014	Oct. 31, 2013
Income Tax [Line Items]
Maximum percentage of tax benefits realized upon ultimate settlement	50.00%
Effective income tax rate	30.90%	33.10%
Decreases in unrecognized tax benefits resulting from effective settlement	$ 4,506
Income tax benefit related to gross uncertain tax benefit releases, net	2,387
Interest and penalties related to uncertain tax benefits	146
Expected decrease in unrecognized tax benefits due to resolution of uncertain tax positions	2,560,000
Expected decrease in interest and penalties due to resolution of uncertain tax positions	385,000
Minimum
Income Tax [Line Items]
Expected gross unrecognized tax benefits decrease	100,000
Expected decrease in interest and penalties	150,000
Maximum
Income Tax [Line Items]
Expected gross unrecognized tax benefits decrease	2,700,000
Expected decrease in interest and penalties	$ 1,200,000