Costs and Estimated Earnings in Excess of Billings (Details) - USD ($) $ in Thousands	Jan. 27, 2018	Jul. 29, 2017	Jul. 30, 2016
Contractors [Abstract]
Costs incurred on contracts in progress	$ 333,775	$ 327,312	$ 307,826
Estimated to date earnings	72,720	92,781	92,226
Total costs and estimated earnings	406,495	420,093	400,052
Less: billings to date	(43,503)	(40,091)	(42,637)
Total costs in excess of billings	362,992	380,002	357,415
Included in the accompanying consolidated balance sheets under the captions:
Costs and estimated earnings in excess of billings	369,472	389,286	376,972
Billings in excess of costs and estimated earnings	(6,480)	(9,284)	(19,557)
Total costs in excess of billings	$ 362,992	$ 380,002	$ 357,415