Revenue and Contract Receivables, , Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 27, 2018	Oct. 28, 2017
Disaggregation of Revenue [Abstract]
Gross revenue	$ 21,752	$ 26,105
U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	18,011	20,835
South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	3,741	5,270
Time and Materials [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	9,267	9,951
Time and Materials [Member] | U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	9,257	9,951
Time and Materials [Member] | South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	0	0
Fixed Price [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	7,353	9,600
Fixed Price [Member] | U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	3,612	4,330
Fixed Price [Member] | South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	3,741	5,270
Cost-Plus [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	5,142	6,554
Cost-Plus [Member] | U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	5,142	6,554
Cost-Plus [Member] | South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	$ 0	$ 0