Costs and Estimated Earnings in Excess of Billings (Details) - USD ($) $ in Thousands	Apr. 29, 2017	Jul. 30, 2016
Contractors [Abstract]
Costs incurred on contracts in progress	$ 373,504	$ 307,826
Estimated to date earnings	100,814	92,226
Total costs and estimated earnings	474,318	400,052
Less: billings to date	(48,308)	(42,637)
Total costs in excess of billings	426,010	357,415
Costs and estimated earnings in excess of billings	440,895	376,972
Billings in excess of costs and estimated earnings	$ (14,885)	$ (19,557)