Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 27, 2012	Jan. 28, 2011	Jan. 27, 2012	Jan. 28, 2011
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 25,609	$ 28,777	$ 49,411	$ 52,511
Other comprehensive income [Abstract]
Change in fair value of interest rate swaps, net of tax expense of $312 and a tax benefit of $2,349, respectively	2,412	9,393	6,362	9,576
Total comprehensive income	28,021	38,170	55,773	62,087
Tax benefit (expense) related to interest rate swaps	$ 120	$ (3,427)	$ (192)	$ (1,078)