Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
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		6,976	0
Contingent consideration	211	11	374
Loss (gain) on sale of assets	(47)	0	(52)
Operating income	85,583	50,083	41,850
Interest expense	962	777	1,857
Other (income) expense, net	(286)	12	(148)
Income from operations before income taxes	84,907	49,294	40,141
Provision for income taxes	16,231	8,740	6,663
Net income (loss)	68,676	40,554	33,478
Net (income) loss attributable to noncontrolling interest	(2,018)	1,045	(272)
Comprehensive income (loss) attributable to IES Holdings, Inc.	$ 66,658	$ 41,599	$ 33,206
Earnings (loss) per share, basic	$ 3.19	$ 1.96	$ 1.56
Earnings (loss) per share, diluted	$ 3.15	$ 1.94	$ 1.55
Weighted Average Number of Shares Outstanding, Basic	20,790,307	20,795,892	21,082,012
Weighted Average Number of Shares Outstanding, Diluted	21,086,432	21,092,410	21,315,245