Per Share Information EPS (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
Continuing operations
Net Income (Loss) from Available to Common Stockholders, Basic									$ 13,275	$ 119,722	$ 16,792
Minority Interest Change In Redemption Value									44
ContinuingNetIncomeLossAvailableToCommonStockholdersDiluted									103	1,056	85
Income (Loss) from Continuing Operations Attributable to Parent									13,422	120,778	16,877
Discontinued operations
DiscontinuedNetIncomeLossAvailableToCommonStockholdersBasic									0	0	(339)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									0	0	(339)
Net Income (Loss) Available to Common Stockholders									13,275	119,722	16,453
Minority Interest Change In Redemption Value									44
Net income (loss) attributable to restricted shareholders									103	1,056	85
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
Weighted Average Number of Shares Outstanding, Basic									21,280,549	21,279,342	21,480,622
Incremental Common Shares Attributable to Share-based Payment Arrangements									252,705	212,997	45,566
Weighted Average Number of Shares Outstanding, Diluted, Total									21,533,254	21,492,339	21,526,188
Earnings Per Share, Basic [Abstract]
Continuing operations									$ 0.62	$ 5.63	$ 0.79
Discontinued operations									0	0	(0.02)
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 [Abstract]
Continuing operations									0.62	5.62	0.79
Discontinued operations									0	0	(0.02)
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