Debt - Senior Subordinated Notes - Loss on Extinguishment (Details) - USD ($)		6 Months Ended	12 Months Ended
	Oct. 15, 2015	Jan. 27, 2018	Jul. 29, 2017	Jul. 30, 2016	Jul. 25, 2015	Oct. 24, 2015	Jul. 15, 2015
Debt Instrument [Line Items]
Loss on debt extinguishment		$ 0	$ 0	$ (16,260,000)	$ 0
Write-off of deferred financing fees and premium on long-term debt		$ 0	$ 0	$ 2,017,000	$ 0
7.125% Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, face amount							$ 277,500,000.0
Debt, interest rate (in percent)				7.125%	7.125%	7.125%	7.125%
Increase in accrued interest	$ 4,900,000
Redemption price, percentage	103.563%
Redemption premium	$ 14,200,000
Loss on debt extinguishment				$ 16,300,000
gain on the extinguishment of debt	6,500,000
Write-off of deferred financing fees and premium on long-term debt	$ 4,900,000