Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Revenues	$ 876,828	$ 810,744	$ 695,993
Cost of services	726,866	670,246	569,013
Gross profit	149,962	140,498	126,980
Selling, general and administrative expenses	123,920	120,370	100,558
Contingent consideration	103	(145)	652
(Gain) loss on sale of assets	(15)	(69)	810
Operating income	25,954	20,342	24,960
Interest and other (income) expense:
Interest expense	1,946	1,702	1,282
Other (income) expense, net	(340)	(165)	(83)
Income from operations before income taxes	24,348	18,805	23,761
Provision (benefit) for income taxes	38,151	5,211	(97,117)
Net income (loss)	(13,803)	13,594	120,878
Net income attributable to noncontrolling interest	354	172	100
Comprehensive income (loss) attributable to IES Holdings, Inc.	$ (14,157)	$ 13,422	$ 120,778
Earnings (loss) per share attributable to IES Holdings, Inc.:
Basic	$ (0.67)	$ 0.62	$ 5.63
Diluted	$ (0.67)	$ 0.62	$ 5.62
Shares used in the computation of income (loss) per share:
Basic	21,196,388	21,280,549	21,279,342
Diluted	21,196,388	21,533,254	21,492,339