Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues	$ 1,076,996	$ 876,828	$ 810,744
Cost of services	894,893	726,866	670,246
Gross profit	182,103	149,962	140,498
Selling, general and administrative expenses	140,575	123,920	120,370
Contingent consideration	(374)	103	(145)
Loss (gain) on sale of assets	52	(15)	(69)
Operating income (loss)	41,850	25,954	20,342
Interest Expense, Debt	1,857	1,946	1,702
Other (income) expense, net	(148)	(340)	(165)
Income (loss) from operations before income taxes	40,141	24,348	18,805
Provision for (benefit from) income taxes	6,663	38,151	5,211
Net income (loss)	33,478	(13,803)	13,594
Net income attributable to noncontrolling interest	(272)	(354)	(172)
Comprehensive income attributable to IES Holdings, Inc.	$ 33,206	$ (14,157)	$ 13,422
Earnings Per Share, Basic	$ 1.56	$ (0.67)	$ 0.62
Earnings Per Share, Diluted	$ 1.55	$ (0.67)	$ 0.62
Weighted Average Number of Shares Outstanding, Basic	21,082,012	21,196,388	21,280,549
Weighted Average Number of Shares Outstanding, Diluted	21,315,245	21,196,388	21,533,254