Fair Value of Option Grant Assumptions (Detail) (USD $)	3 Months Ended				9 Months Ended
	Apr. 30, 2015		Apr. 30, 2014		Apr. 30, 2015		Apr. 30, 2014
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 3 months 22 days	[1]	5 years 4 months 13 days	[1]
Expected volatility			35.10%	[2]	29.30%	[2]	38.60%	[2]
Risk-free interest rate			1.51%	[3]	1.82%	[3]	1.77%	[3]
Expected annual dividend yield			0.42%	[4]	0.56%	[4]	0.52%	[4]
Weighted average grant date fair value			$ 30.80		$ 19.95		$ 27.55
Total Shareholders Return Performance-based Awards
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Stock Price	$ 87.50	[5]	$ 94.32	[5]	$ 71.33	[5]	$ 77.14	[5]
Expected volatility	27.60%	[6]	27.50%	[6]	29.30%	[6]	27.60%	[6]
Risk-free interest rate	0.83%	[7]	0.46%	[7]	1.00%	[7]	0.82%	[7]
Expected annual dividend yield	0.00%	[8]	0.00%	[8]	0.00%	[8]	0.00%	[8]
Weighted average grant date fair value of performance based restricted stock awards	$ 127.52		$ 117.61		$ 88.00		$ 93.85

[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 for periods equal to the expected term of the stock option is based on the U.S. Treasury yield curve in effect at the time of grant.

[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 for periods equal to the performance period is based on the U.S. Treasury yield curve in effect at the time of grant.

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