Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 03, 2021
Cover [Abstract]
Entity Registrant Name	BUILDERS FIRSTSOURCE, INC.
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Trading Symbol	BLDR
Security Exchange Name	NYSE
Entity Central Index Key	0001316835
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Common stock, par value $0.01 per share
Entity Common Stock, Shares Outstanding		207,208,436
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-40620
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-2084569
Entity Address, Address Line One	2001 Bryan Street
Entity Address, Address Line Two	Suite 1600
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75201
City Area Code	214
Local Phone Number	880-3500
Document Quarterly Report	true
Document Transition Report	false