Per Share Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Undistributed Earnings (Loss) Available to Common Shareholders, Basic	$ 66,287	$ 40,830	$ 32,950
Noncontrolling Interest, Period Increase (Decrease)	(315)	(194)	0
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic	(56)	(575)	(256)
Comprehensive income (loss) attributable to IES Holdings, Inc.	$ 66,658	$ 41,599	$ 33,206
Weighted Average Number of Shares Outstanding, Basic	20,790,307	20,795,892	21,082,012
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	296,125	296,518	233,233
Weighted Average Number of Shares Outstanding, Diluted	21,086,432	21,092,410	21,315,245
Earnings (loss) per share, basic	$ 3.19	$ 1.96	$ 1.56
Earnings (loss) per share, diluted	$ 3.15	$ 1.94	$ 1.55