Basis of Presentation and Accounting Policies (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Jul. 25, 2015 USD ($) segment shares	Apr. 25, 2015 USD ($)	Jan. 24, 2015 USD ($)	Oct. 25, 2014 USD ($)	Jul. 26, 2014 USD ($)	Apr. 26, 2014 USD ($)	Jan. 25, 2014 USD ($)	Oct. 26, 2013 USD ($)	Jul. 30, 2016	Jul. 25, 2015 USD ($) shares	Jul. 26, 2014 USD ($)	Jul. 27, 2013 USD ($)
Segment Reporting Information [Line Items]
Prepaid Expense and Other Assets	$ 13,600									$ 13,600
Deferred Finance Costs, Net	$ 11,600									11,600
Number of reportable segments | segment	1
Contract revenues	$ 578,479	$ 492,363	$ 441,081	$ 510,389	$ 482,071	$ 426,284	$ 390,518	$ 512,720		$ 2,022,312	$ 1,811,593	$ 1,608,612
Fiscal period duration										364 days	364 days	364 days
Restricted cash	4,500				4,000					$ 4,500	$ 4,000
Capitalized computer software net book value	21,800				16,500					21,800	16,500
Accrued insurance	87,300				66,000					87,300	66,000
Accrued insurance incurred	39,400				32,100					39,400	32,100
Accrued insurance claims	$ 35,824				$ 32,260					$ 35,824	$ 32,260
Debt, interest rate (in percent)	7.125%				7.125%					7.125%	7.125%	7.125%
Investments and other noncurrent assets		$ 4,000
Senior Subordinated Notes | 7.125% Senior Subordinated Notes Due 2021
Segment Reporting Information [Line Items]
Debt, interest rate (in percent)	7.125%				7.125%					7.125%	7.125%
Canada
Segment Reporting Information [Line Items]
Contract revenues										$ 13,100	$ 12,200	$ 13,000
Long Term Incentive Plan, 2012
Segment Reporting Information [Line Items]
Total number of shares available for grant | shares	1,170,808									1,170,808
RSUs
Segment Reporting Information [Line Items]
Vesting period										4 years
Performance RSUs
Segment Reporting Information [Line Items]
Vesting period										3 years
Stock Options
Segment Reporting Information [Line Items]
Vesting period										4 years
Expiration period										10 years
Subsequent Event
Segment Reporting Information [Line Items]
Fiscal period duration									371 days