Basis of Presentation and Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jan. 27, 2018	Jul. 29, 2017	Jul. 30, 2016	Jul. 25, 2015
Accounting Policies [Abstract]
Insurance recoveries for accrued insurance claims	$ 6,722	$ 9,243	$ 5,714
Maximum \| Revenue Recognized Using Cost To Cost Percentage of Completion Method
Revenue from External Customer [Line Items]
Percentage of Revenue	5.00%	5.00%	5.00%	5.00%

Carrying amount due after one year of the balance sheet date (or one operating cycle, if longer) of amount due in settlement of a claim for reimbursement from an insurance company when the Company has suffered a loss covered under an insurance policy.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_InsuranceSettlementsReceivableNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant