Revenue and Contract Receivables, net, Contract Receivable Concentrations (Details) - USD ($) $ in Thousands	Apr. 27, 2019	Jul. 31, 2018
Contract Receivable Concentrations [Abstract]
Total billed and unbilled contract receivables	$ 25,940	$ 26,899
Allowance for doubtful accounts	1,171	1,284
U.S. Operations [Member]
Contract Receivable Concentrations [Abstract]
Total billed and unbilled contract receivables	20,340	21,580
Allowance for doubtful accounts	$ 505	569
Contract receivables	2.00%
South American Operations [Member]
Contract Receivable Concentrations [Abstract]
Total billed and unbilled contract receivables	$ 5,600	5,319
Allowance for doubtful accounts	$ 666	$ 715
Contract receivables	12.00%

For unclassified balance sheet, amounts due from customers or clients for goods or services that have been delivered or sold in the normal course of business.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(9))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(5))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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