DEI Document - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 01, 2021	Mar. 31, 2021
Entity Information [Line Items]
Entity Registrant Name	IES Holdings, Inc.
Document Type	10-K
Document Period End Date	Sep. 30, 2021
Entity File Number	001-13783
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Amendment Flag	false
Entity Central Index Key	0001048268
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--09-30
Entity Tax Identification Number	76-0542208
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	IESC
Security Exchange Name	NASDAQ
Entity Filer Category	Accelerated Filer
Entity Address, Address Line One	5433 Westheimer Road
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77056
City Area Code	713
Local Phone Number	860-1500
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding			20,702,565
Documents Incorporated by Reference	Certain information contained in the Proxy Statement for the 2022 Annual Meeting of Stockholders of the Registrant to be held on February 24, 2022, is incorporated by reference into Part III of this Annual Report on Form 10-K.
Entity Public Float				$ 450,900
Goodwill, Acquired During Period	$ 38,632	$ 10,117
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Residential [Member]
Entity Information [Line Items]
Goodwill, Acquired During Period	$ 35,151	$ 6,201