Supplemental Consolidating Financial Statements - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jul. 25, 2015	Apr. 25, 2015	Jan. 24, 2015	Oct. 25, 2014	Jul. 26, 2014	Apr. 26, 2014	Jan. 25, 2014	Oct. 26, 2013	Jul. 25, 2015	Jul. 26, 2014	Jul. 27, 2013
Revenues [Abstract]
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
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	446,114	388,239	355,429	403,468	387,221	350,352	327,353	410,119	1,593,250	1,475,045	1,300,416
General and administrative									178,700	161,858	145,771
Depreciation and amortization									96,044	92,772	85,481
Intercompany charges (income), net									0	0	0
Total									1,867,994	1,729,675	1,531,668
Interest expense, net									(27,025)	(26,827)	(23,334)
Other income, net									8,291	11,228	4,589
Income before income taxes									135,584	66,319	58,199
Total provision for income taxes									51,260	26,341	23,011
Net income (loss) before equity in earnings of subsidiaries									84,324	39,978	35,188
Equity in earnings of subsidiaries									0	0	0
Net income	$ 33,827	$ 20,258	$ 9,432	$ 20,807	$ 16,489	$ 7,895	$ (3,067)	$ 18,660	84,324	39,978	35,188
Foreign currency translation losses, net of tax									(1,040)	(261)	(35)
Comprehensive income									83,284	39,717	35,153
Parent
Revenues [Abstract]
Contract revenues									0	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization									0	0	0
General and administrative									52,496	42,958	44,462
Depreciation and amortization									5,471	4,256	2,920
Intercompany charges (income), net									(65,098)	(53,922)	(53,377)
Total									(7,131)	(6,708)	(5,995)
Interest expense, net									(7,012)	(6,827)	(5,675)
Other income, net									(119)	119	(320)
Income before income taxes									0	0	0
Total provision for income taxes									0	0	0
Net income (loss) before equity in earnings of subsidiaries									0	0	0
Equity in earnings of subsidiaries									84,324	39,978	35,188
Net income									84,324	39,978	35,188
Foreign currency translation losses, net of tax									(1,040)	(261)	(35)
Comprehensive income									83,284	39,717	35,153
Issuer
Revenues [Abstract]
Contract revenues									0	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization									0	0	0
General and administrative									540	616	818
Depreciation and amortization									0	0	0
Intercompany charges (income), net									0	0	0
Total									540	616	818
Interest expense, net									(20,003)	(19,993)	(17,599)
Other income, net									0	0	0
Income before income taxes									(20,543)	(20,609)	(18,417)
Total provision for income taxes									(7,769)	(8,186)	(7,281)
Net income (loss) before equity in earnings of subsidiaries									(12,774)	(12,423)	(11,136)
Equity in earnings of subsidiaries									97,098	52,401	46,324
Net income									84,324	39,978	35,188
Foreign currency translation losses, net of tax									(1,040)	(261)	(35)
Comprehensive income									83,284	39,717	35,153
Guarantor Subsidiaries
Revenues [Abstract]
Contract revenues									2,009,258	1,799,538	1,594,363
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization									1,583,651	1,466,221	1,288,369
General and administrative									113,329	107,326	89,336
Depreciation and amortization									85,696	84,178	77,595
Intercompany charges (income), net									67,430	54,688	54,720
Total									1,850,106	1,712,413	1,510,020
Interest expense, net									(10)	(7)	(60)
Other income, net									9,039	10,895	4,794
Income before income taxes									168,181	98,013	89,077
Total provision for income taxes									63,560	38,930	35,214
Net income (loss) before equity in earnings of subsidiaries									104,621	59,083	53,863
Equity in earnings of subsidiaries									0	135	0
Net income									104,621	59,218	53,863
Foreign currency translation losses, net of tax									0	0	0
Comprehensive income									104,621	59,218	53,863
Non- Guarantor Subsidiaries
Revenues [Abstract]
Contract revenues									13,054	12,055	14,249
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization									9,599	8,824	12,047
General and administrative									12,335	10,958	11,155
Depreciation and amortization									4,877	4,338	4,966
Intercompany charges (income), net									(2,332)	(766)	(1,343)
Total									24,479	23,354	26,825
Interest expense, net									0	0	0
Other income, net									(629)	214	115
Income before income taxes									(12,054)	(11,085)	(12,461)
Total provision for income taxes									(4,531)	(4,403)	(4,922)
Net income (loss) before equity in earnings of subsidiaries									(7,523)	(6,682)	(7,539)
Equity in earnings of subsidiaries									0	0	0
Net income									(7,523)	(6,682)	(7,539)
Foreign currency translation losses, net of tax									(1,040)	(261)	(35)
Comprehensive income									(8,563)	(6,943)	(7,574)
Eliminations and Reclassifications
Revenues [Abstract]
Contract revenues									0	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization									0	0	0
General and administrative									0	0	0
Depreciation and amortization									0	0	0
Intercompany charges (income), net									0	0	0
Total									0	0	0
Interest expense, net									0	0	0
Other income, net									0	0	0
Income before income taxes									0	0	0
Total provision for income taxes									0	0	0
Net income (loss) before equity in earnings of subsidiaries									0	0	0
Equity in earnings of subsidiaries									(181,422)	(92,514)	(81,512)
Net income									(181,422)	(92,514)	(81,512)
Foreign currency translation losses, net of tax									2,080	522	70
Comprehensive income									$ (179,342)	$ (91,992)	$ (81,442)