Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Jan. 24, 2015	Jul. 26, 2014
Loss Contingencies [Line Items]
Construction liens	$ 17.7dy_ConstructionLiens
Loss Contingency, Damages Sought	2.6
Credit Agreement, December 3, 2012, Maturing December 2017 \| Senior Credit Agreement - Revolving facility (matures December 2017) \| Standby Letters of Credit
Loss Contingencies [Line Items]
Letters of credit outstanding amount	54.4	49.4
Performance Guarantee and Surety Bond
Loss Contingencies [Line Items]
Outstanding performance and other surety contract bonds	393.2	446.8
Other Accrued Liabilities
Loss Contingencies [Line Items]
Settlement liability	$ 0.6

Construction liens on outstanding accounts receivable.

No definition available.

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

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ 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

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

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Describes the form and magnitude of the award the plaintiff seeks in the legal matter, which may include an unspecified amount of money.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

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- Definition

Amounts payable for money transfers, money orders, and consumer payment service arrangements. Settlement liabilities include amounts payable to intermediaries for global payment transfers.

+ References

No definition available.

+ Details

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

- Details

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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