Other Accrued Liabilities (Details) (USD $)	Apr. 25, 2015	Jul. 26, 2014
Payables and Accruals [Abstract]
Accrued payroll and related taxes	$ 16,974,000us-gaap_AccruedPayrollTaxesCurrent	$ 18,429,000us-gaap_AccruedPayrollTaxesCurrent
Accrued employee benefit and incentive plan costs	21,060,000us-gaap_AccruedEmployeeBenefitsCurrent	17,677,000us-gaap_AccruedEmployeeBenefitsCurrent
Accrued construction costs	21,175,000dy_AccruedConstructionCostsCurrent	20,689,000dy_AccruedConstructionCostsCurrent
Accrued interest and related bank fees	5,591,000dy_AccruedInterestAndRelatedBankFees	872,000dy_AccruedInterestAndRelatedBankFees
Other current liabilities	13,424,000us-gaap_OtherLiabilitiesCurrent	18,467,000us-gaap_OtherLiabilitiesCurrent
Total other accrued liabilities	78,224,000us-gaap_OtherAccruedLiabilitiesCurrent	76,134,000us-gaap_OtherAccruedLiabilitiesCurrent
Accrued income taxes for other current liabilities		$ 5,200,000us-gaap_AccruedIncomeTaxesCurrent

Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Carrying value as of the balance sheet date of obligations incurred and payable for statutory payroll taxes incurred through that date and withheld from employees pertaining to services received from them, including entity's matching share of the employees FICA taxes and contributions to the state and federal unemployment insurance programs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable arising from transactions not otherwise specified in the taxonomy. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

Aggregate carrying amount of current liabilities (due within one year or within the normal operating cycle if longer) not separately disclosed in the balance sheet. Includes costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered and of liabilities not separately disclosed.

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