Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 293,607	$ 282,633	$ 256,914	$ 243,842	$ 240,275	$ 232,576	$ 205,677	$ 198,300	$ 1,076,996	$ 876,828	$ 810,744
Gross profit	50,870	46,397	43,235	41,601	40,521	42,537	33,840	33,064	182,103	149,962	140,498
Net income (loss) attributable to IES Holdings, Inc.	$ 9,861	$ 10,972	$ 5,489	$ 6,884	$ 4,675	$ 8,516	$ 2,221	$ (29,569)	$ 33,206	$ (14,157)	$ 13,422
Earnings Per Share, Basic	$ 0.47	$ 0.52	$ 0.26	$ 0.32	$ 0.22	$ 0.40	$ 0.11	$ (1.39)	$ 1.56	$ (0.67)	$ 0.62
Earnings Per Share, Diluted	$ 0.46	$ 0.52	$ 0.26	$ 0.32	$ 0.22	$ 0.40	$ 0.11	$ (1.39)	$ 1.55	$ (0.67)	$ 0.62