Capital Stock (Details) - USD ($)				3 Months Ended	6 Months Ended		12 Months Ended
	Feb. 23, 2016	Sep. 15, 2015	Aug. 25, 2015	Jan. 23, 2016	Jan. 23, 2016	Jan. 24, 2015	Jul. 25, 2015	Jul. 26, 2014
Class of Stock [Line Items]
Number of shares repurchased		805,000		954,224			1,669,924
Total Consideration (Dollars in thousands)				$ 69,997,000	$ 69,997,000	$ 17,147,000	$ 87,146,000
Average Price Per Share (in dollars per share)		$ 74.53		$ 73.35			$ 52.19
Stock repurchased and retired during period, value		$ 60,000,000
Share repurchase program, additional amount authorized for repurchase			$ 50,000,000.0
Remaining authorized repurchase amount				$ 50,000,000	$ 50,000,000
Stock repurchase program, period in force			18 months
Stock repurchase program, authorized amount			$ 50,000,000
Shares paid for tax withholding for share based compensation							156,362	138,535
Value of shares paid for tax withholding for share based compensation							$ 12,100,000	$ 4,300,000
Subsequent Event [Member]
Class of Stock [Line Items]
Share repurchase program, additional amount authorized for repurchase	$ 50,000,000
Remaining authorized repurchase amount	$ 100,000,000
Stock repurchase program, period in force extension	6 months
Stock repurchase program, authorized amount	$ 100,000,000