Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Revenue Recognition and Deferred Revenue [Abstract]
Unbilled Receivables, Current	$ 9,753		$ 9,753
Costs and estimated earnings in excess of billings	44,469		44,469		$ 52,076
Billings in excess of costs and estimated earnings	(109,119)		(109,119)		$ (84,936)
Contract with Customer, Liability, Revenue Recognized			78,263	$ 46,703
Performance Obligation Next 12 Months	856,542		856,542
Revenue, Remaining Performance Obligation, Amount	1,071,605		1,071,605
Disaggregation of Revenue [Line Items]
Revenues	584,451	$ 567,301	1,728,206	1,549,403
Contract with Customer, Liability, Revenue Recognized			78,263	46,703
Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	67,768	80,953	197,068	219,016
Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	141,615	144,748	429,980	402,776
Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	57,057	39,837	158,957	123,666
Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	318,011	301,763	942,201	803,945
Fixed-price Contract [Member]
Disaggregation of Revenue [Line Items]
Revenues	532,798	509,777	1,552,702	1,395,686
Fixed-price Contract [Member] | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	61,351	75,779	178,902	204,985
Fixed-price Contract [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	98,027	94,109	277,693	268,253
Fixed-price Contract [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	55,409	38,126	153,906	118,503
Fixed-price Contract [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	318,011	301,763	942,201	803,945
Time-and-materials Contract [Member]
Disaggregation of Revenue [Line Items]
Revenues	51,653	57,524	175,504	153,717
Time-and-materials Contract [Member] | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	6,417	5,174	18,166	14,031
Time-and-materials Contract [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	43,588	50,639	152,287	134,523
Time-and-materials Contract [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,648	1,711	5,051	5,163
Time-and-materials Contract [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
industrial Services [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	11,312	15,317	33,828	45,970
Custom Power Solutions [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	45,745	24,520	125,129	77,696
Single Family Contracts [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	228,637	224,556	666,891	590,453
Multi Family and Other [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 89,374	$ 77,207	$ 275,310	$ 213,492