Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenues	$ 1,190,856	$ 1,076,996	$ 876,828
Cost of services	962,897	894,893	726,866
Gross profit	227,959	182,103	149,962
Selling, general and administrative expenses	170,911	140,575	123,920
Goodwill impairment expense	6,976	0	0
Contingent consideration	11	374	103
Loss (gain) on sale of assets	0	52	(15)
Operating income	50,083	41,850	25,954
Interest expense	777	1,857	1,946
Other (income) expense, net	12	(148)	(340)
Income from operations before income taxes	49,294	40,141	24,348
Provision for income taxes	8,740	6,663	38,151
Net income (loss)	40,554	33,478	(13,803)
Net (income) loss attributable to noncontrolling interest	1,045	(272)	(354)
Comprehensive income (loss) attributable to IES Holdings, Inc.	$ 41,599	$ 33,206	$ (14,157)
Earnings (loss) per share, basic	$ 1.96	$ 1.56	$ (0.67)
Earnings (loss) per share, diluted	$ 1.94	$ 1.55	$ (0.67)
Weighted Average Number of Shares Outstanding, Basic	20,795,892	21,082,012	21,196,388
Weighted Average Number of Shares Outstanding, Diluted	21,092,410	21,315,245	21,196,388