Quarterly Results Of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Quarterly Results Of Operations (Unaudited) [Abstract]
Revenues	$ 206,581	$ 208,323	$ 203,662	$ 192,178	$ 205,647	$ 179,599	$ 159,981	$ 150,766	$ 810,744	$ 695,993	$ 573,857
Gross Profit	38,104	35,398	31,814	35,182	37,538	33,997	27,812	27,633	140,498	126,980	99,891
Net Income Attributable to IES Holdings	$ 3,146	$ 5,868	$ 536	$ 3,872	$ 101,980	$ 10,805	$ 2,194	$ 5,799	$ 13,422	$ 120,778	$ 16,538
Earnings Per Share, Basic	$ 0.15	$ 0.27	$ 0.02	$ 0.18	$ 4.75	$ 0.5	$ 0.1	$ 0.27	$ 0.62	$ 5.63	$ 0.77
Earnings Per Share, Diluted	$ 0.14	$ 0.27	$ 0.02	$ 0.18	$ 4.74	$ 0.5	$ 0.1	$ 0.27	$ 0.62	$ 5.62	$ 0.77