v3.26.1
Employee Stock-Based Compensation - Additional Information (Detail) - $ / shares
6 Months Ended
May 14, 2026
Jun. 30, 2026
2026 Equity Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of shares reserved for share based compensation award   3,600,000
Stock based compensation equity incentive plan description   common stock for the grant of awards under the 2026 Plan, subject to adjustment as provided by the 2026 Plan, and less one share for every one share subject to an award granted under the Builders FirstSource, Inc. 2014 Incentive Plan (the “2014 Plan”) after March 1, 2026 and prior to May 14, 2026.
Stock award granted vested period   3 years
Shares available for issuance   2,500,000
Number of additional shares available for future issuance   300,000
2026 Equity Incentive Plan | Cliff Vest    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Stock award granted vested period   3 years
Employee Stock Purchase Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of shares reserved for share based compensation award 2,500,000  
Stock based compensation purchase price of common stock, percent 85.00%  
Share based compensation arrangement by share based payment award, shares issued in period   0
Time Based Restricted Stock Unit Grants    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Weighted average grant date fair value, granted   $ 89.18
Time Based Restricted Stock Unit Grants | Minimum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Stock award granted vested period   1 year
Time Based Restricted Stock Unit Grants | Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Stock award granted vested period   3 years
Time Based Restricted Stock Unit Grants | 2014 Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
RSUs Granted   575,000
Performance Market and Service Condition Based Restricted Stock Unit Grants | 2014 Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
RSUs Granted   218,500
Stock award granted vested period   3 years
Weighted average grant date fair value, granted   $ 88.88
Performance Market and Service Condition Based Restricted Stock Unit Grants | 2014 Incentive Plan | Minimum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Percentage of number of shares of common stock earned   0.00%
Performance Market and Service Condition Based Restricted Stock Unit Grants | 2014 Incentive Plan | Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Percentage of number of shares of common stock earned   200.00%
Performance Market and Service Condition Based Restricted Stock Unit Grants | 2026 Equity Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Increased percentage of total number of shares of additional common stock earned   10.00%
Decreased percentage of total number of shares of additional common stock earned   10.00%
Stock Options and SARS | 2026 Equity Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Granted term   10 years