Revenue and Contract Receivables, net, Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 27, 2019	Apr. 28, 2018	Apr. 27, 2019	Apr. 28, 2018
Disaggregation of Revenue [Abstract]
Gross revenue	$ 21,775	$ 20,677	$ 63,780	$ 68,071
U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	16,935	16,565	51,250	53,784
South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	4,840	4,112	12,530	14,287
Time and Materials [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	10,699	10,038	29,689	28,826
Time and Materials [Member] | U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	10,699	10,038	29,689	28,826
Time and Materials [Member] | South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	0	0	0	0
Fixed Price [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	7,728	7,360	21,975	24,623
Fixed Price [Member] | U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	2,888	3,248	9,445	10,336
Fixed Price [Member] | South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	4,840	4,112	12,530	14,287
Cost-Plus [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	3,348	3,279	12,116	14,622
Cost-Plus [Member] | U.S. Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	3,348	3,279	12,116	14,622
Cost-Plus [Member] | South American Operations [Member]
Disaggregation of Revenue [Abstract]
Gross revenue	$ 0	$ 0	$ 0	$ 0