Acquisitions - Schedule of Supplemental Pro Forma Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2025
Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]
Revenue	$ 795,369	$ 1,478,106
Net income (loss) attributable to Legence	$ (7,790)	$ (39,351)

Amount, after tax, of pro forma income (loss) of combined entity as if acquisition date of business combination occurred as of beginning of period.

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