Document and Entity Information - shares	3 Months Ended
	Oct. 28, 2017	Nov. 19, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	DYCOM INDUSTRIES INC
Entity Central Index Key	0000067215
Current Fiscal Year End Date	--01-27
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Oct. 28, 2017
Entity Common Stock, Shares Outstanding		30,938,786