v3.26.1
Noncontrolling Interests - Schedule of Ownership of Legence Holdings (Details) - Legence Holdings LLC - shares
 3 Months Ended
Jun. 30, 2026
Mar. 31, 2026
Dec. 31, 2025
Noncontrolling Interest [Line Items]      
Common unit, outstanding (in shares) 108,037,932 105,336,929  
Issuance of Class A Common Stock for acquisitions (in shares)   2,701,003  
Effects of exercise of underwriters' overallotment option (in shares) 0 0  
Issuance of Class A Common Stock for vested RSUs (in shares) 14,493    
Common unit, outstanding (in shares) 108,052,425 108,037,932  
Legence's ownership of Legence Holdings Common Units (as percent) 100.00% 100.00% 100.00%
Issuance of Class A Common Stock for acquisitions   0.00%  
Effects of exercise of underwriters' overallotment option 0.00% 0.00%  
Issuance of Class A Common Stock for vested RSUs (as percent) 0.00%    
LGN A Units      
Noncontrolling Interest [Line Items]      
Common unit, outstanding (in shares) 67,338,099 63,856,975  
Issuance of Class A Common Stock for acquisitions (in shares)   2,701,003  
Effects of exercise of underwriters' overallotment option (in shares) 9,528,699 780,121  
Issuance of Class A Common Stock for vested RSUs (in shares) 14,493    
Common unit, outstanding (in shares) 76,881,291 67,338,099  
Legence's ownership of Legence Holdings Common Units (as percent) 71.20% 62.30% 60.60%
Issuance of Class A Common Stock for acquisitions   1.00%  
Effects of exercise of underwriters' overallotment option 8.90% 0.70%  
Issuance of Class A Common Stock for vested RSUs (as percent) 0.00%    
LGN B Units      
Noncontrolling Interest [Line Items]      
Common unit, outstanding (in shares) 40,699,833 41,479,954  
Issuance of Class A Common Stock for acquisitions (in shares)   0  
Effects of exercise of underwriters' overallotment option (in shares) (9,528,699) (780,121)  
Issuance of Class A Common Stock for vested RSUs (in shares) 0    
Common unit, outstanding (in shares) 31,171,134 40,699,833  
Legacy Owners ownership of Legence Holdings Common Units (as percent) 28.80% 37.70% 39.40%
Issuance of Class A Common Stock for acquisitions   (1.00%)  
Effects of exercise of underwriters' overallotment option (8.90%) (0.70%)  
Issuance of Class A Common Stock for vested RSUs (as percent) 0.00%