Document And Entity Information (USD $)	9 Months Ended
	Apr. 28, 2012	Jan. 29, 2011
Entity Registrant Name	DYCOM INDUSTRIES INC
Entity Central Index Key	0000067215
Current Fiscal Year End Date	--07-28
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float		$ 538,163,860
Entity Common Stock, Shares Outstanding	33,593,696
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Apr. 28, 2012