Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Revenues	$ 256,914	$ 205,677	$ 500,756	$ 403,977
Cost of services	213,679	171,837	415,920	337,073
Gross profit	43,235	33,840	84,836	66,904
Selling, general and administrative expenses	35,070	29,647	67,156	59,736
Contingent consideration	(149)	71	(115)	71
Loss (gain) on sale of assets	98	(20)	95	(34)
Operating income	8,216	4,142	17,700	7,131
Interest and other (income) expense:
Interest expense	535	473	1,082	914
Other income, net	(112)	(43)	(65)	(141)
Income from operations before income taxes	7,793	3,712	16,683	6,358
Provision for income taxes	2,336	1,425	4,243	33,584
Net income (loss)	5,457	2,287	12,440	(27,226)
Net (income) loss attributable to noncontrolling interest	32	(66)	(67)	(122)
Comprehensive income (loss) attributable to IES Holdings, Inc.	$ 5,489	$ 2,221	$ 12,373	$ (27,348)
Earnings (loss) per share attributable to IES Holdings, Inc.:
Basic	$ 0.26	$ 0.11	$ 0.58	$ (1.29)
Diluted	$ 0.26	$ 0.11	$ 0.58	$ (1.29)
Shares used in the computation of earnings (loss) per share
Basic	21,139,096	21,182,268	21,187,834	21,189,641
Diluted	21,379,746	21,440,570	21,424,522	21,189,641