Fair Value of Option Grant Assumptions (Detail) - $ / shares		12 Months Ended
		Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option term in years	[1]	5 years 3 months 22 days	5 years 4 months 13 days	5 years 5 months 1 day
Expected volatility	[2]	29.30%	38.60%	41.00%
Risk-free interest rate	[3]	1.82%	1.77%	0.80%
Expected annual dividend yield	[4]	0.56%	0.52%	0.57%
Weighted average grant date fair value		$ 19.95	$ 27.55	$ 25.25
Total Shareholders Return Performance-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Price	[5]	$ 71.33	$ 77.14	$ 70.04
Expected volatility	[6]	29.30%	27.60%	28.00%
Risk-free interest rate	[7]	1.00%	0.82%	0.32%
Expected annual dividend yield	[8]	0.00%	0.00%	0.00%
Total Shareholders Return Performance-based Awards | Time Based Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of performance based restricted stock awards		$ 73.23	$ 82.46	$ 71.78
Total Shareholders Return Performance-based Awards | Performance Based Restricted Stock Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of performance based restricted stock awards		$ 78.62	$ 93.85	$ 85.94

[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%.