Business and Organization	12 Months Ended
Business and Organization	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Organization	Business and Organization Powell Industries, Inc. (we, us, our, Powell or the Company) was incorporated in the state of Delaware in 2004 as a successor to a Nevada company incorporated in 1968. The Nevada company was the successor to a company founded by William E. Powell in 1947, which merged into the Company in 1977. Our major subsidiaries, all of which are wholly owned, include: Powell Electrical Systems, Inc.; Powell (UK) Limited; Powell Canada Inc.; and Powell Industries International, B.V. We develop, design, manufacture and service custom-engineered equipment and systems which (1) distribute, control and monitor the flow of electrical energy and (2) provide protection to motors, transformers and other electrically powered equipment. Our principal products include integrated power control room substations (PCRs®), custom-engineered modules, electrical houses (E-Houses), traditional and arc-resistant distribution switchgear and control gear, medium-voltage circuit breakers, monitoring and control communications systems, motor control centers, switches and bus duct systems. These products are designed for application voltages ranging from 480 volts to 38,000 volts and are used in oil and gas refining, onshore and offshore oil and gas production, petrochemical, liquefied natural gas (LNG) terminals, pipeline, terminal, mining and metals, light rail traction power, electric utility, pulp and paper and other heavy industrial markets. Our product scope includes designs tested to meet both U.S. and international standards, under both the American National Standards Institute (ANSI) and International Electrotechnical Commission. We assist customers by providing value-added services such as spare parts, field service inspection, installation, commissioning, modification and repair, retrofit and retrofill components for existing systems and replacement circuit breakers for switchgear that is obsolete or that is no longer produced by the original manufacturer. We seek to establish long-term relationships with the end users of our systems as well as the design and construction engineering firms contracted by those end users. We believe that our culture of safety and focus on customer satisfaction, along with our financial strength, allow us to continue to capitalize on opportunities in the industries we serve. References to Fiscal 2020, Fiscal 2019 and Fiscal 2018 used throughout these Notes to Consolidated Financial Statements relate to our fiscal years ended September 30, 2020, 2019 and 2018, respectively. Impact of the COVID-19 Pandemic and Oil and Gas Commodity Market Volatility on Powell The spread of COVID-19 has created significant uncertainty and economic disruption across the world during the second half of Fiscal 2020 and continuing into Fiscal 2021. This pandemic has negatively impacted energy demand, which in turn has resulted in considerable volatility across the oil and gas commodity markets. As a result, some of our industrial customers are deferring or suspending their planned capital expenditures. Certain of our customers have asked that we delay our manufacturing on their projects as their operations have been negatively impacted by this pandemic and the reduced oil and gas demand. We continue to work with and review the contracts with our key suppliers who have been impacted by this pandemic to ensure that we are able to meet our customer commitments. From an operational standpoint, although our facilities are located in areas that have been or continue to be subject to stay-at-home orders, we have not closed any of our facilities for an extended amount of time and have continued to operate as an "essential business" under these orders across all of our locations. We continue to take the necessary steps to ensure the safety of our employees, customers and vendors. These steps include, among others, promoting increased social distancing practices and enhanced cleaning efforts in our offices and facilities. We are also using technology across our operations to further enhance social distancing and improve safety. These increased safety precautions may have an adverse impact on our efficiency and productivity going forward. As a result of the circumstances noted above, we anticipate that a decrease in commercial activity will negatively impact our business, results of operations and cash flows going forward. We have and may need to continue to adjust our workforce and labor costs to correspond to the reduced customer demand. We will take prudent measures to maintain our strong liquidity and cash position, which may include reducing our capital expenditures and research and development costs, as well as reducing or eliminating future dividend payments. However, the extent to which the COVID-19 pandemic specifically will impact our business will depend on numerous factors that are hard to predict, some of which include: the duration, spread and severity of the pandemic; governmental actions in response to the pandemic, including travel restrictions and quarantine or related governmental orders; any closures of our offices and facilities or those of our suppliers as a result of the pandemic, and how quickly and to what extent normal economic and operating conditions can resume. Therefore, the magnitude of the impact on our business, results of operations and cash flows is not currently known.