Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 04, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-36050
Entity Registrant Name	BMC Stock Holdings, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-4687975
Entity Address, Address Line One	8020 Arco Corporate Drive, Suite 400
Entity Address, City or Town	Raleigh,
Entity Address, State or Province	NC
Entity Address, Postal Zip Code	27617
City Area Code	919
Local Phone Number	431-1000
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	BMCH
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		66,749,662
Entity Central Index Key	0001574815
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Current Fiscal Year End Date	--12-31