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Accounts Receivable Contract Assets and Liabilities (Details) - USD ($) $ in Thousands | Apr. 28, 2018 | Jan. 27, 2018
--- | --- | ---
Receivables [Abstract] |  |
Contract assets | $ 101,163 | $ 369,472
Contract liabilities | 5,730 | 6,480
Contract assets, net | $ 95,433 | $ 362,992

X
- Definition Contract With Customer Asset Net + References No definition available. + Details
Name: | dy_ContractWithCustomerAssetNet
Namespace Prefix: | dy_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Contract with Customer, Asset, Gross + References No definition available. + Details
Name: | dy_ContractwithCustomerAssetGross
Namespace Prefix: | dy_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Contract with Customer, Liability + References No definition available. + Details
Name: | dy_ContractwithCustomerLiability
Namespace Prefix: | dy_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration