Supplemental Consolidating Financial Statements Income Statement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Oct. 27, 2012	Oct. 29, 2011
Revenues [Abstract]
Contract revenues	$ 323,286	$ 319,575
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	257,066	255,187
General and administrative	28,824	25,358
Depreciation and amortization	15,311	15,958
Intercompany charges (income), net	0	0
Total	301,201	296,503
Interest expense, net	(4,197)	(4,173)
Other income, net	1,614	2,959
INCOME BEFORE INCOME TAXES	19,502	21,858
PROVISION (BENEFIT) FOR INCOME TAXES	7,641	8,892
NET INCOME (LOSS) BEFORE EQUITY IN EARNINGS OF SUBSIDIARIES	11,861	12,966
EQUITY IN EARNINGS OF SUBSIDIARIES	0	0
NET INCOME	11,861	12,966
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	2	(87)
COMPREHENSIVE INCOME (LOSS)	11,863	12,879
Parent
Revenues [Abstract]
Contract revenues	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	0	0
General and administrative	8,409	6,407
Depreciation and amortization	740	787
Intercompany charges (income), net	(9,925)	(7,964)
Total	(776)	(770)
Interest expense, net	(776)	(770)
Other income, net	0	0
INCOME BEFORE INCOME TAXES	0	0
PROVISION (BENEFIT) FOR INCOME TAXES	0	0
NET INCOME (LOSS) BEFORE EQUITY IN EARNINGS OF SUBSIDIARIES	0	0
EQUITY IN EARNINGS OF SUBSIDIARIES	11,861	12,966
NET INCOME	11,861	12,966
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	2	(87)
COMPREHENSIVE INCOME (LOSS)	11,863	12,879
Issuer
Revenues [Abstract]
Contract revenues	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	0	0
General and administrative	146	147
Depreciation and amortization	0	0
Intercompany charges (income), net	0	0
Total	146	147
Interest expense, net	(3,420)	(3,414)
Other income, net	0	0
INCOME BEFORE INCOME TAXES	(3,566)	(3,561)
PROVISION (BENEFIT) FOR INCOME TAXES	(1,397)	(1,440)
NET INCOME (LOSS) BEFORE EQUITY IN EARNINGS OF SUBSIDIARIES	(2,169)	(2,121)
EQUITY IN EARNINGS OF SUBSIDIARIES	14,030	15,087
NET INCOME	11,861	12,966
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	2	(87)
COMPREHENSIVE INCOME (LOSS)	11,863	12,879
Subsidiary Guarantors
Revenues [Abstract]
Contract revenues	319,025	313,818
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	253,544	250,893
General and administrative	17,616	16,404
Depreciation and amortization	13,286	13,861
Intercompany charges (income), net	10,272	7,496
Total	294,718	288,654
Interest expense, net	(1)	11
Other income, net	1,565	3,061
INCOME BEFORE INCOME TAXES	25,871	28,236
PROVISION (BENEFIT) FOR INCOME TAXES	10,136	11,476
NET INCOME (LOSS) BEFORE EQUITY IN EARNINGS OF SUBSIDIARIES	15,735	16,760
EQUITY IN EARNINGS OF SUBSIDIARIES	0	0
NET INCOME	15,735	16,760
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	0	0
COMPREHENSIVE INCOME (LOSS)	15,735	16,760
Non-Guarantor Subsidiaries
Revenues [Abstract]
Contract revenues	4,261	5,757
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	3,522	4,294
General and administrative	2,653	2,400
Depreciation and amortization	1,285	1,322
Intercompany charges (income), net	(347)	468
Total	7,113	8,484
Interest expense, net	0	0
Other income, net	49	(102)
INCOME BEFORE INCOME TAXES	(2,803)	(2,829)
PROVISION (BENEFIT) FOR INCOME TAXES	(1,098)	(1,144)
NET INCOME (LOSS) BEFORE EQUITY IN EARNINGS OF SUBSIDIARIES	(1,705)	(1,685)
EQUITY IN EARNINGS OF SUBSIDIARIES	0	0
NET INCOME	(1,705)	(1,685)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	2	(87)
COMPREHENSIVE INCOME (LOSS)	(1,703)	(1,772)
Eliminations and Reclassifications
Revenues [Abstract]
Contract revenues	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	0	0
General and administrative	0	0
Depreciation and amortization	0	(12)
Intercompany charges (income), net	0	0
Total	0	(12)
Interest expense, net	0	0
Other income, net	0	0
INCOME BEFORE INCOME TAXES	0	12
PROVISION (BENEFIT) FOR INCOME TAXES	0	0
NET INCOME (LOSS) BEFORE EQUITY IN EARNINGS OF SUBSIDIARIES	0	12
EQUITY IN EARNINGS OF SUBSIDIARIES	(25,891)	(28,053)
NET INCOME	(25,891)	(28,041)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(4)	174
COMPREHENSIVE INCOME (LOSS)	$ (25,895)	$ (27,867)