Fair Value of Option Granted Valuation Assumption (Detail) - Stock Options	9 Months Ended
	Apr. 30, 2015 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option term in years	5 years 3 months 22 days	[1]
Expected volatility	29.30%	[2]
Risk-free interest rate	1.82%	[3]
Expected annual dividend yield	0.56%	[4]
Weighted average grant date fair value	$ 19.95

[1] The expected option term was estimated using historical data.

[2] The expected volatility for each grant is determined based on the review of the average of historical daily price changes of our common stock over the expected option term.

[3] The risk-free interest rate is determined based on the yield of zero-coupon U.S. Treasury securities for a period that is commensurate with the expected term assumption.

[4] The expected annual dividend yield is calculated by dividing the expected annual dividends by the stock price on the date of grant.