ACCOUNTING POLICIES (Details) (USD $)	3 Months Ended								12 Months Ended
	Jul. 28, 2012	Apr. 28, 2012	Jan. 28, 2012	Oct. 29, 2011	Jul. 30, 2011	Apr. 30, 2011	Jan. 29, 2011	Oct. 30, 2010	Jul. 28, 2012	Jul. 30, 2011	Jul. 31, 2010
Business Acquisitions [Line Items]
Amount of purchase price on acquisition placed into escrow							$ 900,000
Number of weeks in fiscal year (in weeks)									52	52	53
Number of weeks in fourth quarter (in weeks)											14
Restricted Cash [Abstract]
Restricted cash	3,700,000				4,700,000				3,700,000	4,700,000
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	11,600,000				8,000,000				11,600,000	8,000,000
Property, Plant and Equipment, Net	7,400,000				5,800,000				7,400,000	5,800,000
Accrued Insurance, Incurred but not reported losses	22,300,000				22,700,000				22,300,000	22,700,000
Accrued Insurance Claims Current	25,218,000				26,092,000				25,218,000	26,092,000
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	187,500,000				187,574,000				187,500,000	187,574,000
Segment Reporting Information [Line Items]
Contract revenues	318,034,000	296,103,000	267,407,000	319,575,000	303,719,000	252,363,000	218,203,000	261,584,000	1,201,119,000	1,035,868,000	988,623,000
Total number of shares available for grant (in shares)	914,180								914,180
Debt Instrument [Line Items]
Interest rate (in hundredths)	7.125%				8.125%				7.125%	8.125%
Senior Subordinated Notes 2021 [Member]
Debt Instrument [Line Items]
Interest rate (in hundredths)	7.125%								7.125%
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)									4 years
Exercisable Period									10 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)									4 years
Performance Restricted Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)									3 years
Performance Period									3 years
Canada [Member]
Segment Reporting Information [Line Items]
Contract revenues									11,900,000	7,400,000	6,300,000
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	192,000,000				190,500,000				192,000,000	190,500,000
Communication Services [Member]
Business Acquisitions [Line Items]
Acquisition price							9,000,000
Capital lease obligations assumed							900,000
NeoCom [Member]
Business Acquisitions [Line Items]
Acquisition price							$ 27,500,000