Credit Agreement Liquidity Requirement

No definition available.

Name:	dy_CreditAgreementLiquidityRequirement
Namespace Prefix:	dy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Instrument, Covenant Compliance, Consolidated Interest Coverage Ratio

+ References

No definition available.

+ Details

Name:	dy_DebtInstrumentCovenantComplianceConsolidatedInterestCoverageRatio
Namespace Prefix:	dy_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Covenant Compliance, Consolidated Leverage Ratio

+ References

No definition available.

+ Details

Name:	dy_DebtInstrumentCovenantComplianceConsolidatedLeverageRatio
Namespace Prefix:	dy_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Outstanding Debt Credit Agreement Threshold

+ References

No definition available.

+ Details

Name:	dy_OutstandingDebtCreditAgreementThreshold
Namespace Prefix:	dy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unrestricted Cash and Cash Equivalents Credit Agreement Threshold

+ References

No definition available.

+ Details

Name:	dy_UnrestrictedCashandCashEquivalentsCreditAgreementThreshold
Namespace Prefix:	dy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=dy_IncrementalFacilityMinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=dy_A0.75ConvertibleSeniorNotesDue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Senior Credit Agreement (Details)		12 Months Ended
Debt - Senior Credit Agreement (Details)	Sep. 15, 2015 USD ($)	Jan. 26, 2019 USD ($)	Oct. 19, 2018 USD ($)	Jan. 27, 2018 USD ($)
Line of Credit Facility [Line Items]
Letters of credit outstanding amount		$ 48,600,000		$ 48,600,000
Additional borrowing availability		412,900,000		401,400,000
Standby Letters of Credit
Line of Credit Facility [Line Items]
Long-term Line of Credit		0		0
Line of Credit Facility, Maximum Borrowing Capacity			$ 200,000,000
Letters of credit outstanding amount		48,600,000
Incremental Facility, Minimum
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 350,000,000
Credit Agreement - Term Loan (matures April 2020)
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			450,000,000
Debt Instrument, Covenant Compliance, Consolidated Leverage Ratio	2.25
Unrestricted Cash and Cash Equivalents Credit Agreement Threshold		$ 50,000,000.0
Credit Agreement - Revolving facility (matures April 2020)
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 450,000,000		$ 750,000,000.0
Maximum [Member]
Line of Credit Facility [Line Items]
Debt instrument, covenant compliance, consolidated interest coverage ratio, maximum		1.00
Debt Instrument, Covenant Compliance, Consolidated Leverage Ratio		1.00
Minimum
Line of Credit Facility [Line Items]
Debt instrument, covenant compliance, consolidated interest coverage ratio, maximum		3.00
Debt Instrument, Covenant Compliance, Consolidated Leverage Ratio		3.50
0.75% Convertible Senior Notes Due 2021
Line of Credit Facility [Line Items]
Credit Agreement Liquidity Requirement		$ 150,000,000.0
Debt instrument, face amount	$ 485,000,000.0	485,000,000		$ 485,000,000
Outstanding Debt Credit Agreement Threshold		$ 250,000,000.0