Document and Entity Information - shares	3 Months Ended
	Apr. 27, 2019	May 20, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	DYCOM INDUSTRIES INC
Entity Central Index Key	0000067215
Current Fiscal Year End Date	--01-25
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Document Type	10-Q
Entity Emerging Growth Company	false
Entity Small Business	false
Amendment Flag	false
Document Period End Date	Apr. 27, 2019
Entity Common Stock, Shares Outstanding		31,482,973