Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2021
Revenue Recognition and Deferred Revenue [Abstract]
Unbilled Receivables, Current	$ 21,824		$ 21,824
Costs and estimated earnings in excess of billings	55,517		55,517		$ 43,389
Billings in excess of costs and estimated earnings	(63,619)		(63,619)		$ (62,486)
Contract with Customer, Liability, Revenue Recognized	38,349	$ 28,385	45,115	$ 33,740
Performance Obligation Next 12 Months	792,953		792,953
Revenue, Remaining Performance Obligation, Amount	835,548		835,548
Disaggregation of Revenue [Line Items]
Revenues	501,593	331,961	982,102	646,799
Contract with Customer, Liability, Revenue Recognized	38,349	28,385	45,115	33,740
Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	68,815	52,023	138,063	114,613
Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	130,639	94,886	258,028	193,242
Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	41,733	34,716	83,829	69,117
Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	260,406	150,336	502,182	269,827
Fixed-price Contract [Member]
Disaggregation of Revenue [Line Items]
Revenues	450,398	300,849	885,909	589,705
Fixed-price Contract [Member] | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	64,346	49,003	129,206	109,690
Fixed-price Contract [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	85,722	68,551	174,144	144,565
Fixed-price Contract [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	39,924	32,959	80,377	65,623
Fixed-price Contract [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	260,406	150,336	502,182	269,827
Time-and-materials Contract [Member]
Disaggregation of Revenue [Line Items]
Revenues	51,195	31,112	96,193	57,094
Time-and-materials Contract [Member] | Commercial and Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	4,469	3,020	8,857	4,923
Time-and-materials Contract [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Revenues	44,917	26,335	83,884	48,677
Time-and-materials Contract [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,809	1,757	3,452	3,494
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	15,837	10,548	30,653	20,588
Custom Power Solutions [Member] | Infrastructure Solutions [Member]
Disaggregation of Revenue [Line Items]
Revenues	25,896	24,168	53,176	48,529
Single Family Contracts [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	192,368	100,476	365,896	172,602
Multi Family and Other [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 68,038	$ 49,860	$ 136,286	$ 97,225