Document And Entity Information - shares	2 Months Ended
	Dec. 31, 2018	Feb. 05, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	NCI BUILDING SYSTEMS INC
Entity Central Index Key	0000883902
Trading Symbol	NCS
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-QT
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q4
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		125,475,859