Income Taxes - Components of Income Tax (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jul. 29, 2017	Jul. 30, 2016	Jul. 25, 2015
Current:
Federal	$ (4,384)		$ 62,455	$ 42,096	$ 42,516
Foreign	598		176	310	502
State	1,166		12,344	8,399	6,998
Current Income Tax Expense (Benefit)	(2,620)		74,975	50,805	50,016
Deferred:
Federal	(21,332)		17,051	26,467	305
Foreign	(37)		(35)	(296)	268
State	1,704		1,217	611	671
Deferred income tax (benefit) provision	(19,665)		18,233	26,782	1,244
Total provision for income taxes	$ (22,285)	$ 44,332	$ 93,208	$ 77,587	$ 51,260