| Cover | Dec. 08, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Dec. 8, 2020 |
| Entity Registrant Name | POWELL INDUSTRIES, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-12488 |
| Entity Tax Identification Number | 88-0106100 |
| Entity Address, Address Line One | 8550 Mosley Road |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77075-1180 |
| City Area Code | 713 |
| Local Phone Number | 944-6900 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | POWL |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0000080420 |
