Document and Entity Information - shares	9 Months Ended
	Jun. 30, 2019	Aug. 05, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	POWELL INDUSTRIES INC
Entity Central Index Key	0000080420
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		11,566,748