Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2021
Revenue Recognition and Deferred Revenue [Abstract]
Unbilled Receivables, Current	$ 17,651		$ 17,651
Costs and estimated earnings in excess of billings	58,728		58,728		$ 43,389
Billings in excess of costs and estimated earnings	(71,397)		(71,397)		$ (62,486)
Contract with Customer, Liability, Revenue Recognized	30,204	$ 25,851	46,703	$ 41,121
Performance Obligation Next 12 Months	852,181		852,181
Revenue, Remaining Performance Obligation, Amount	893,923		893,923
Disaggregation of Revenue [Line Items]
Revenues	567,301	405,871	1,549,403	1,052,670
Contract with Customer, Liability, Revenue Recognized	30,204	25,851	46,703	41,121
Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	80,953	64,087	219,016	178,700
Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	144,748	116,218	402,776	309,460
Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	39,837	39,117	123,666	108,234
Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	301,763	186,449	803,945	456,276
Fixed-price Contract [Member]
Disaggregation of Revenue [Line Items]
Revenues	509,777	365,655	1,395,686	955,360
Fixed-price Contract [Member] | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	75,779	60,444	204,985	170,134
Fixed-price Contract [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	94,109	81,521	268,253	226,086
Fixed-price Contract [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	38,126	37,241	118,503	102,864
Fixed-price Contract [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	301,763	186,449	803,945	456,276
Time-and-materials Contract [Member]
Disaggregation of Revenue [Line Items]
Revenues	57,524	40,216	153,717	97,310
Time-and-materials Contract [Member] | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	5,174	3,643	14,031	8,566
Time-and-materials Contract [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	50,639	34,697	134,523	83,374
Time-and-materials Contract [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,711	1,876	5,163	5,370
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	15,317	11,972	45,970	32,560
Custom Power Solutions [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	24,520	27,145	77,696	75,674
Single Family Contracts [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	224,556	102,105	590,453	274,707
Multi Family and Other [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 77,207	$ 84,344	$ 213,492	$ 181,569