Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]
Stockholders' Equity Attributable to Parent at Sep. 30, 2019	$ 246,248	$ 220	$ (12,483)	$ 192,911	$ 65,600
Shares, Issued at Sep. 30, 2019		22,049,529	884,518
Issuances under compensation plans			$ 1,343	(1,343)
Issuances under compensation plans, shares			95,409
Acquisition of treasury stock	(858)		$ (858)	0
Acquisition of treasury stock, shares			(37,244)
Non-cash compensation	931			931
Noncontrolling Interest, Change in Redemption Value	(45)				(45)
Net income (loss) attributable to IES Holdings, Inc.	8,502				8,502
Stockholders' Equity Attributable to Parent at Dec. 31, 2019	254,778	$ 220	$ (11,998)	192,499	74,057
Shares, Issued at Dec. 31, 2019		22,049,529	826,353
Stockholders' Equity Attributable to Parent at Sep. 30, 2020	283,313	$ 220	$ (24,499)	200,587	107,005
Shares, Issued at Sep. 30, 2020		22,049,529	1,287,134
Issuances under compensation plans			$ 741	(741)
Issuances under compensation plans, shares			38,467
Acquisition of treasury stock	(695)		$ (1,226)	531
Acquisition of treasury stock, shares			(30,878)
Non-cash compensation	842			842
Noncontrolling Interest, Change in Redemption Value	118				118
Net income (loss) attributable to IES Holdings, Inc.	12,098				12,098
Stockholders' Equity Attributable to Parent at Dec. 31, 2020	295,462	$ 220	$ (24,984)	$ 201,219	119,007
Shares, Issued at Dec. 31, 2020		22,049,529	1,279,545
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ (214)				$ (214)