Derivative Instruments and Hedging Activities, Pre-tax Effects of Derivative Instruments on AOCIL and Income (Details) - Interest Rate Swaps [Member] - Cash Flow Hedging [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 27, 2018	Apr. 28, 2017	Apr. 27, 2018	Apr. 28, 2017	Jul. 28, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income recognized in AOCIL on derivatives (effective portion)			$ 12,779		$ 15,402
Ineffectiveness recorded in earnings on interest rate cash flow hedge			0	$ 0
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss reclassified from AOCIL into income (effective portion)	$ 865	$ 993	$ 2,852	$ 3,354