Other Current Assets and Other Assets - Current (Details) - USD ($) $ in Thousands	Jan. 27, 2018	Jul. 29, 2017	Jul. 30, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 13,167	$ 10,588	$ 8,249
Insurance recoveries for accrued insurance claims	13,701	0	0
Receivables on equipment sales	31	2,761	913
Deposits and other current assets, including restricted cash	12,811	10,254	6,944
Total other current assets	39,710	23,603	16,106
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Income tax receivable	$ 13,852	$ 7,493	0
Other Current Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Income tax receivable			$ 1,400