Debt (Details) - USD ($)	12 Months Ended
Debt (Details) - USD ($)	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Debt Disclosure [Abstract]
Long-term debt	$ 0	$ 0
Debt Issuance Costs, Noncurrent, Net	2,597,000	598,000
Letters of Credit Outstanding, Amount	5,545,000
Line of Credit Facility, Remaining Borrowing Capacity	294,455,000
Loans Payable	$ 0	0
ControllingShareholderOwnershipPercentage	54.00%
Line of Credit Facility [Line Items]
Net income (loss) attributable to IES Holdings, Inc.	$ 305,975,000	219,116,000	$ 108,288,000
Loans Payable	$ 0	$ 0

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

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