Costs and Estimated Earnings in Excess of Billings (Details) - USD ($) $ in Thousands	Jul. 25, 2015	Jul. 26, 2014
Contractors [Abstract]
Costs incurred on contracts in progress	$ 240,077	$ 234,766
Estimated to date earnings	72,446	57,335
Total costs and estimated earnings	312,523	292,101
Less: billings to date	(54,689)	(75,414)
Total costs in excess of billings	257,834	216,687
Costs and estimated earnings in excess of billings	274,730	230,569
Billings in excess of costs and estimated earnings	(16,896)	(13,882)
Total costs in excess of billings	$ 257,834	$ 216,687