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Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jan. 25, 2014 | Jan. 26, 2013 | Jan. 25, 2014 | Jan. 26, 2013
Related Party Transaction [Line Items] |  |  |  |
Subcontracting Expense, Related Party | $ 0.3 | $ 0.2 | $ 0.6 | $ 0.3
Total expense under lease agreements | $ 0.6 | $ 0.4 | $ 1.2 | $ 0.8

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- Definition Subcontracting expenses during the period with related parties. + References No definition available. + Details
Name: | dy_SubcontractingExpenseRelatedParty
Namespace Prefix: | dy_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 + Details
Name: | us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration