Document and Entity Information (USD $)	12 Months Ended
	Sep. 30, 2011	Dec. 01, 2011	Mar. 31, 2011
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, 2011
Amendment Flag	false
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 462,404,000
Entity Common Stock, Shares Outstanding		11,766,981