Supplementary Balance Sheet Information (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 180,800	$ 156,800	$ 144,000
Amortization of Intangible Assets	8,300	$ 4,700	$ 5,100
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	3,000
Estimated amortization expense for intangible assets, year two	3,000
Estimated amortization expense for intangible assets, year three	3,000
Estimated amortization expense for intangible assets, year four	3,000
Estimated amortization expense for intangible assets, year five	$ 3,000