Accounting Standards - Narratives (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jan. 27, 2018	Jan. 26, 2019	Jul. 29, 2017	Jul. 30, 2016	Jan. 27, 2019	Jan. 28, 2018	Jul. 25, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted Cash	$ 6,200		$ 5,400	$ 5,000			$ 4,500
Payment for Debt Extinguishment or Debt Prepayment Cost, financing	0	$ 0	$ 0	14,243
Accounts Receivable, Net, Current	318,684	625,258				$ 630,400
Contract with Customer, Asset, Gross	$ 369,472	215,849				57,800
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Net, Current		341,795
Contract with Customer, Asset, Gross		499,312
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Net, Current		283,463				$ 311,700
Contract with Customer, Asset, Gross		$ (283,463)
Scenario, Forecast | Subsequent Event | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset					$ 70,000
Operating Lease, Liability					70,000
Scenario, Forecast | Subsequent Event | Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset					75,000
Operating Lease, Liability					$ 75,000
Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Payment for Debt Extinguishment or Debt Prepayment Cost, financing				$ 14,200