Supplemental Consolidating Financial Statements - Income Statement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Apr. 25, 2015	Apr. 26, 2014	Apr. 25, 2015	Apr. 26, 2014
Revenues [Abstract]
Contract revenues	$ 492,363us-gaap_SalesRevenueServicesNet	$ 426,284us-gaap_SalesRevenueServicesNet	$ 1,443,833us-gaap_SalesRevenueServicesNet	$ 1,329,522us-gaap_SalesRevenueServicesNet
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	388,239	350,352	1,147,136	1,087,824
General and administrative	44,707us-gaap_GeneralAndAdministrativeExpense	39,162us-gaap_GeneralAndAdministrativeExpense	131,218us-gaap_GeneralAndAdministrativeExpense	120,799us-gaap_GeneralAndAdministrativeExpense
Depreciation and amortization	23,985	22,726	70,179	69,713
Intercompany charges (income), net	0dy_IntercompanyChargesIncome	0dy_IntercompanyChargesIncome	0dy_IntercompanyChargesIncome	0dy_IntercompanyChargesIncome
Interest expense, net	(6,646)us-gaap_InterestIncomeExpenseNet	(6,563)us-gaap_InterestIncomeExpenseNet	(20,126)us-gaap_InterestIncomeExpenseNet	(20,249)us-gaap_InterestIncomeExpenseNet
Other income, net	3,471us-gaap_OtherNonoperatingIncomeExpense	5,593us-gaap_OtherNonoperatingIncomeExpense	7,001us-gaap_OtherNonoperatingIncomeExpense	8,200us-gaap_OtherNonoperatingIncomeExpense
Income before income taxes	32,257	13,074	82,175	39,137
Provision (benefit) for income taxes:	11,999us-gaap_IncomeTaxExpenseBenefit	5,179us-gaap_IncomeTaxExpenseBenefit	31,678us-gaap_IncomeTaxExpenseBenefit	15,649us-gaap_IncomeTaxExpenseBenefit
Net income (loss) before equity in earnings of subsidiaries	20,258	7,895	50,497	23,488
Equity in earnings (losses) of subsidiaries	0dy_EquityInEarningsOfSubsidiaries	0dy_EquityInEarningsOfSubsidiaries	0dy_EquityInEarningsOfSubsidiaries	0dy_EquityInEarningsOfSubsidiaries
Net income	20,258us-gaap_NetIncomeLoss	7,895us-gaap_NetIncomeLoss	50,497us-gaap_NetIncomeLoss	23,488us-gaap_NetIncomeLoss
Foreign currency translation gains (losses), net of tax	38	(46)	(688)	(332)
Comprehensive income	20,296us-gaap_ComprehensiveIncomeNetOfTax	7,849us-gaap_ComprehensiveIncomeNetOfTax	49,809us-gaap_ComprehensiveIncomeNetOfTax	23,156us-gaap_ComprehensiveIncomeNetOfTax
Parent
Revenues [Abstract]
Contract revenues	0	0	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	0	0	0	0
General and administrative	13,249	9,878	38,056	31,398
Depreciation and amortization	1,410	1,164	3,953	3,058
Intercompany charges (income), net	(16,294)	(12,608)	(47,124)	(39,713)
Interest expense, net	(1,635)	(1,566)	(5,115)	(5,260)
Other income, net	0	0	0	3
Income before income taxes	0	0	0	0
Provision (benefit) for income taxes:	0	0	0	0
Net income (loss) before equity in earnings of subsidiaries	0	0	0	0
Equity in earnings (losses) of subsidiaries	20,258	7,895	50,497	23,488
Net income	20,258	7,895	50,497	23,488
Foreign currency translation gains (losses), net of tax	38	(46)	(688)	(332)
Comprehensive income	20,296	7,849	49,809	23,156
Issuer
Revenues [Abstract]
Contract revenues	0	0	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	0	0	0	0
General and administrative	131	211	371	651
Depreciation and amortization	0	0	0	0
Intercompany charges (income), net	0	0	0	0
Interest expense, net	(5,002)	(4,997)	(15,001)	(14,985)
Other income, net	0	0	0	0
Income before income taxes	(5,133)	(5,208)	(15,372)	(15,636)
Provision (benefit) for income taxes:	(1,889)	(2,063)	(5,926)	(6,252)
Net income (loss) before equity in earnings of subsidiaries	(3,244)	(3,145)	(9,446)	(9,384)
Equity in earnings (losses) of subsidiaries	23,502	11,040	59,943	32,872
Net income	20,258	7,895	50,497	23,488
Foreign currency translation gains (losses), net of tax	38	(46)	(688)	(332)
Comprehensive income	20,296	7,849	49,809	23,156
Subsidiary Guarantors
Revenues [Abstract]
Contract revenues	490,351	423,853	1,434,010	1,321,684
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	386,689	348,602	1,139,962	1,081,975
General and administrative	28,552	26,308	83,222	80,574
Depreciation and amortization	21,344	20,506	62,715	63,357
Intercompany charges (income), net	16,877	12,669	48,799	40,049
Interest expense, net	(9)	0	(10)	(4)
Other income, net	3,438	5,554	7,132	8,130
Income before income taxes	40,318	21,322	106,434	63,855
Provision (benefit) for income taxes:	14,965	8,447	41,030	25,533
Net income (loss) before equity in earnings of subsidiaries	25,353	12,875	65,404	38,322
Equity in earnings (losses) of subsidiaries	(10)	70	(261)	70
Net income	25,343	12,945	65,143	38,392
Foreign currency translation gains (losses), net of tax	0	0	0	0
Comprehensive income	25,343	12,945	65,143	38,392
Non- Guarantor Subsidiaries
Revenues [Abstract]
Contract revenues	2,012	2,431	9,823	7,838
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	1,550	1,750	7,174	5,849
General and administrative	2,775	2,765	9,569	8,176
Depreciation and amortization	1,231	1,056	3,511	3,298
Intercompany charges (income), net	(583)	(61)	(1,675)	(336)
Interest expense, net	0	0	0	0
Other income, net	33	39	(131)	67
Income before income taxes	(2,928)	(3,040)	(8,887)	(9,082)
Provision (benefit) for income taxes:	(1,077)	(1,205)	(3,426)	(3,632)
Net income (loss) before equity in earnings of subsidiaries	(1,851)	(1,835)	(5,461)	(5,450)
Equity in earnings (losses) of subsidiaries	0	0	0	0
Net income	(1,851)	(1,835)	(5,461)	(5,450)
Foreign currency translation gains (losses), net of tax	38	(46)	(688)	(332)
Comprehensive income	(1,813)	(1,881)	(6,149)	(5,782)
Eliminations and Reclassifications
Revenues [Abstract]
Contract revenues	0	0	0	0
EXPENSES:
Costs of earned revenues, excluding depreciation and amortization	0	0	0	0
General and administrative	0	0	0	0
Depreciation and amortization	0	0	0	0
Intercompany charges (income), net	0	0	0	0
Interest expense, net	0	0	0	0
Other income, net	0	0	0	0
Income before income taxes	0	0	0	0
Provision (benefit) for income taxes:	0	0	0	0
Net income (loss) before equity in earnings of subsidiaries	0	0	0	0
Equity in earnings (losses) of subsidiaries	(43,750)	(19,005)	(110,179)	(56,430)
Net income	(43,750)	(19,005)	(110,179)	(56,430)
Foreign currency translation gains (losses), net of tax	(76)	92	1,376	664
Comprehensive income	$ (43,826)	$ (18,913)	$ (108,803)	$ (55,766)

Income (Loss) From Investment In Subsidiaries

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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The aggregate cost of services rendered during the reporting period, excluding depreciation, depletion and amortization.

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The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to parent entity.

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The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

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Aggregate revenue during the period from services rendered in the normal course of business, after deducting allowances and discounts.

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