Document and Entity Information - USD ($)	12 Months Ended
	Jan. 26, 2019	Feb. 28, 2019	Jul. 28, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	DYCOM INDUSTRIES INC
Entity Central Index Key	0000067215
Current Fiscal Year End Date	--01-26
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,694,173,840
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Jan. 26, 2019
Entity Common Stock, Shares Outstanding		31,441,024
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false