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

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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

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

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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ 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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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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
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Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
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:	us-gaap_DebtInstrumentAxis=dy_A0.75ConvertibleSeniorNotesDue2021Member
Namespace Prefix:
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Period Type:

Debt - Senior Credit Agreement (Details)		3 Months Ended	12 Months Ended
Debt - Senior Credit Agreement (Details)	Sep. 15, 2015 USD ($)	Apr. 27, 2019 USD ($)	Jan. 26, 2019 USD ($)	Oct. 19, 2018 USD ($)
Line of Credit Facility [Line Items]
Letters of credit outstanding amount		$ 52,300,000	$ 48,600,000
Additional borrowing availability		325,400,000	412,900,000
Standby Letters of Credit
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity				$ 200,000,000
Letters of credit outstanding amount		52,300,000	$ 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 maximum borrowing capacity				450,000,000.0
Debt instrument, covenant compliance, consolidated leverage ratio, maximum	2.25
Unrestricted cash and cash equivalents threshold		$ 50,000,000.0
Credit Agreement - Revolving facility (matures April 2020)
Line of Credit Facility [Line Items]
Line of credit maximum borrowing capacity	$ 450,000,000.0			$ 750,000,000.0
Unutilized commitment fee (in percent)		0.35%	0.35%
Minimum
Line of Credit Facility [Line Items]
Debt instrument, covenant compliance, consolidated leverage ratio, maximum		3.50
Debt instrument, covenant compliance, consolidated interest coverage ratio, maximum		3.00
Minimum \| Standby Letters of Credit
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)		1.25%
Minimum \| Credit Agreement - Revolving facility (matures April 2020)
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)		0.20%
Maximum
Line of Credit Facility [Line Items]
Debt instrument, covenant compliance, consolidated leverage ratio, maximum		1.00
Debt instrument, covenant compliance, consolidated interest coverage ratio, maximum		1.00
Maximum \| Standby Letters of Credit
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)		2.00%
Maximum \| Credit Agreement - Revolving facility (matures April 2020)
Line of Credit Facility [Line Items]
Unutilized commitment fee (in percent)		0.40%
0.75% Convertible Senior Notes Due 2021
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 485,000,000.0	$ 485,000,000	$ 485,000,000
Outstanding debt threshold		250,000,000
Credit agreement liquidity requirement		$ 150,000,000.0