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, Beginning Balance at Sep. 30, 2017	$ 236,704	$ 220	$ 6,898	$ 196,955	$ 46,427
Shares, Issued, Beginning Balance at Sep. 30, 2017		22,049,529	712,554
Issuances under compensation plans	0		$ 5	(5)
Issuances under compensation plans, shares			520
Acquisition of treasury stock	(2,059)		$ (2,059)
Acquisition of treasury stock, shares			(133,459)
Options exercised	$ 11		$ 15	(4)
Options exercised, shares	1,500		1,500
Non-cash compensation	$ (136)			(136)
Decrease (increase) in noncontrolling interest	44				44
Net income (loss) attributable to IES Holdings, Inc.	(14,157)				(14,157)
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2018	220,407	$ 220	$ 8,937	196,810	32,314
Shares, Issued, Ending Balance at Sep. 30, 2018		22,049,529	843,993
Issuances under compensation plans	0		$ 5,942	(5,942)
Issuances under compensation plans, shares			501,797
Acquisition of treasury stock	$ (9,802)		$ (9,802)
Acquisition of treasury stock, shares	(467,819)		(564,822)
Options exercised	$ 0		$ 314	(314)
Options exercised, shares	22,500		22,500
Non-cash compensation	$ 2,357			2,357
Cumulative Effect of New Accounting Principle	80				80
Net income (loss) attributable to IES Holdings, Inc.	33,206				33,206
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2019	$ 246,248	$ 220	$ 12,483	192,911	65,600
Shares, Issued, Ending Balance at Sep. 30, 2019	22,500	22,049,529	884,518
Issuances under compensation plans	$ 0		$ 1,708	(1,708)
Issuances under compensation plans, shares			120,197
Acquisition of treasury stock	$ (7,697)		$ (13,808)	6,111
Acquisition of treasury stock, shares	(263,160)		(528,563)
Options exercised	$ 34		$ 84	(50)
Options exercised, shares	5,750		5,750
Non-cash compensation	$ 3,323			3,323
Decrease (increase) in noncontrolling interest	(194)				(194)
Net income (loss) attributable to IES Holdings, Inc.	41,599				41,599
Stockholders' Equity Attributable to Parent, Ending Balance at Sep. 30, 2020	$ 283,313	$ 220	$ 24,499	$ 200,587	$ 107,005
Shares, Issued, Ending Balance at Sep. 30, 2020	5,750	22,049,529	1,287,134