Fair Value of Option Grant Assumptions (Detail) (USD $)	3 Months Ended				9 Months Ended
	Apr. 30, 2014		Apr. 30, 2013		Apr. 30, 2014		Apr. 30, 2013
Stock Options
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Expected option term in years	5 years 3 months 22 days	[1]	5 years 5 months 19 days	[1]	5 years 4 months 13 days	[1]	5 years 5 months 1 day	[1]
Expected volatility	35.10%	[2]	41.00%	[2]	38.60%	[2]	41.00%	[2]
Risk-free interest rate	1.51%	[3]	0.91%	[3]	1.77%	[3]	0.80%	[3]
Expected annual dividend yield	0.42%	[4]	0.52%	[4]	0.52%	[4]	0.57%	[4]
Total Shareholders Return
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Stock Price	$ 94.32	[5]	$ 70.04	[5]	$ 77.14	[5]	$ 70.04	[5]
Expected volatility	27.50%	[6]	28.00%	[6]	27.60%	[6]	28.00%	[6]
Risk-free interest rate	0.46%	[7]	0.32%	[7]	0.82%	[7]	0.32%	[7]
Expected annual dividend yield	0.00%	[8]	0.00%	[8]	0.00%	[8]	0.00%	[8]

[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.

[5] The stock price is the closing price of our common stock on the date of grant.

[6] The expected volatility for each grant is determined based on the historical volatility for the peer group companies and our common stock over a period equal to the remaining term of the performance period from the date of grant for all awards.

[7] 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 performance period.

[8] Dividends are considered reinvested when calculating TSR. The dividend yield is therefore considered to be 0%.