Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues		$ 1,536,493	$ 1,190,856	$ 1,076,996
Cost of services		1,248,495	962,897	894,893
Gross profit		287,998	227,959	182,103
Selling, general and administrative expenses		202,251	170,911	140,575
Goodwill impairment expense	$ 0		6,976	0
Contingent consideration		(211)	(11)	(374)
Loss (gain) on sale of assets		47	0	52
Operating income (loss)		85,583	50,083	41,850
Depreciation and amortization		21,914	12,508	9,557
Capital expenditures		7,401	4,745	6,300
Total assets	766,622	766,622	560,528	445,258
Communications [Member]
Segment Reporting Information [Line Items]
Revenues		445,968	395,141	321,246
Cost of services		361,197	317,013	264,746
Gross profit		84,771	78,128	56,500
Selling, general and administrative expenses		41,373	37,674	31,850
Goodwill impairment expense			0
Contingent consideration		0	0	97
Loss (gain) on sale of assets		4	(8)	6
Operating income (loss)		43,402	40,446	24,753
Depreciation and amortization		1,394	1,351	1,513
Capital expenditures		963	830	973
Total assets	164,699	164,699	154,808	109,263
Residential [Member]
Segment Reporting Information [Line Items]
Revenues		687,347	411,790	313,336
Cost of services		553,546	318,034	248,562
Gross profit		133,801	93,756	64,774
Selling, general and administrative expenses		92,761	63,668	46,864
Goodwill impairment expense			0
Contingent consideration		(211)	0	0
Loss (gain) on sale of assets		(86)	(2)	17
Operating income (loss)		40,743	30,086	17,927
Depreciation and amortization		11,490	2,276	852
Capital expenditures		2,829	1,459	1,412
Total assets	329,691	329,691	110,998	63,903
Infrastructure Solutions [Member]
Segment Reporting Information [Line Items]
Revenues		146,980	128,379	136,790
Cost of services		106,048	93,358	105,863
Gross profit		40,932	35,021	30,927
Selling, general and administrative expenses		23,966	20,418	18,664
Goodwill impairment expense			0
Contingent consideration		0	0	277
Loss (gain) on sale of assets		10	(35)	(105)
Operating income (loss)		16,976	14,568	12,435
Depreciation and amortization		6,170	6,020	4,528
Capital expenditures		2,067	795	1,377
Total assets	137,628	137,628	124,640	116,867
Commercial and Industrial [Member]
Segment Reporting Information [Line Items]
Revenues		256,198	255,546	305,624
Cost of services		227,704	234,492	275,722
Gross profit		28,494	21,054	29,902
Selling, general and administrative expenses		28,172	32,128	27,815
Goodwill impairment expense		0	6,976
Contingent consideration		0	11	0
Loss (gain) on sale of assets		92	45	30
Operating income (loss)		414	(17,994)	2,117
Depreciation and amortization		2,709	2,768	2,563
Capital expenditures		1,453	1,362	2,402
Total assets	87,577	87,577	68,318	82,050
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Revenues		0	0	0
Cost of services		0	0	0
Gross profit		0	0	0
Selling, general and administrative expenses		15,979	17,023	15,382
Goodwill impairment expense			0
Contingent consideration		0	0	0
Loss (gain) on sale of assets		27	0	0
Operating income (loss)		(15,952)	(17,023)	(15,382)
Depreciation and amortization		151	93	101
Capital expenditures		89	299	136
Total assets	$ 47,027	$ 47,027	$ 101,764	$ 73,175