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, 2018	$ 220,407	$ 220	$ (8,937)	$ 196,810	$ 32,314
Shares, Issued at Sep. 30, 2018		22,049,529	843,993
Issuances under compensation plans			$ 2,252	(2,252)
Issuances under compensation plans, shares			212,688
Acquisition of treasury stock	(2,211)		$ (2,211)	0
Acquisition of treasury stock, shares			(132,121)
Non-cash compensation	(49)			(49)
Noncontrolling Interest, Change in Redemption Value	0
Net income (loss) attributable to IES Holdings, Inc.	6,884				6,884
Stockholders' Equity Attributable to Parent at Dec. 31, 2018	225,231	$ 220	$ (8,896)	194,607	39,300
Shares, Issued at Dec. 31, 2018		22,049,529	763,426
Cumulative Effect of New Accounting Principle in Period of Adoption	102
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)
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