Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Dec. 02, 2016	Mar. 31, 2016
Document And Entity Information [Abstract]
Entity Registrant Name	POWELL INDUSTRIES INC
Entity Central Index Key	0000080420
Document Type	10-K
Document Period End Date	Sep. 30, 2016
Amendment Flag	false
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Trading Symbol	powl
Entity Public Float			$ 339
Entity Common Stock, Shares Outstanding		11,411,638