v3.26.1
Revenue Recognition (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Sep. 30, 2025
Revenue Recognition and Deferred Revenue [Abstract]          
Unbilled Receivables, Current $ 31,187   $ 31,187    
Costs and estimated earnings in excess of billings 120,459   120,459   $ 69,229
Billings in excess of costs and estimated earnings (357,580)   (357,580)   $ (176,782)
Contract with Customer, Liability, Revenue Recognized     164,294 $ 145,991  
Revenue, Remaining Performance Obligation, Amount 2,801,635   2,801,635    
Disaggregation of Revenue [Line Items]          
Revenues 1,242,697 $ 890,158 3,087,939 2,473,665  
Contract with Customer, Liability, Revenue Recognized     164,294 145,991  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]          
Revenue, Remaining Performance Obligation, Amount 2,801,635   2,801,635    
Commercial and Industrial [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 241,395 115,419 462,738 329,268  
Communications [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 453,081 299,213 1,172,697 805,189  
Infrastructure Solutions [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 224,123 129,488 556,746 355,233  
Residential [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 324,098 346,038 895,758 983,975  
Fixed-price Contract [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 1,010,349 779,467 2,516,539 2,177,445  
Fixed-price Contract [Member] | Commercial and Industrial [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 228,724 102,855 424,769 287,474  
Fixed-price Contract [Member] | Communications [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 267,348 211,644 710,699 580,389  
Fixed-price Contract [Member] | Infrastructure Solutions [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 190,179 118,930 485,313 325,607  
Fixed-price Contract [Member] | Residential [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 324,098 346,038 895,758 983,975  
Time-and-materials Contract [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 232,348 110,691 571,400 296,220  
Time-and-materials Contract [Member] | Commercial and Industrial [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 12,671 12,564 37,969 41,794  
Time-and-materials Contract [Member] | Communications [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 185,733 87,569 461,998 224,800  
Time-and-materials Contract [Member] | Infrastructure Solutions [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 33,944 10,558 71,433 29,626  
Time-and-materials Contract [Member] | Residential [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 0 0 0 0  
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-07-01          
Revenue Recognition and Deferred Revenue [Abstract]          
Revenue, Remaining Performance Obligation, Amount 2,289,343   2,289,343    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]          
Revenue, Remaining Performance Obligation, Amount $ 2,289,343   $ 2,289,343    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period 12 months   12 months    
industrial Services [Member] | Infrastructure Solutions [Member]          
Disaggregation of Revenue [Line Items]          
Revenues $ 44,613 23,708 $ 109,492 71,553  
Custom Power Solutions [Member] | Infrastructure Solutions [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 179,510 105,780 447,254 283,680  
Single Family Contracts [Member] | Residential [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 151,373 171,792 422,554 501,074  
Multi Family and Other [Member] | Residential [Member]          
Disaggregation of Revenue [Line Items]          
Revenues 75,476 87,917 203,036 243,221  
Single Family Contracts Plumbing HVAC | Residential [Member]          
Disaggregation of Revenue [Line Items]          
Revenues $ 97,249 $ 86,329 $ 270,168 $ 239,680