Business Segments (Narrative) (Details)	1 Months Ended	12 Months Ended										3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended			3 Months Ended
	Apr. 30, 2013 USD ($)	Sep. 30, 2013 USD ($) segment	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2013 United States USD ($)	Sep. 30, 2012 United States USD ($)	Sep. 30, 2011 United States USD ($)	Sep. 30, 2013 Canada	Sep. 30, 2012 Canada	Sep. 30, 2011 Canada	Sep. 30, 2012 Colombia	Sep. 30, 2013 Powell Canada CAD	Sep. 30, 2011 Powell Canada USD ($)	Jun. 30, 2013 Electrical Power Products USD ($)	Sep. 30, 2013 Electrical Power Products USD ($)	Sep. 30, 2012 Electrical Power Products USD ($)	Sep. 30, 2011 Electrical Power Products USD ($)	Dec. 31, 2011 Electrical Power Products Kazakhstan Joint Venture CAD	Dec. 31, 2011 Electrical Power Products Powell Canada CAD
Number of reportable business segments		2
Gain on sale of investment				$ 1,229,000														1,200,000
Equity investment in Kazakhstan																		50.00%
Loss on impairment of intangible assets													7,200,000						7,200,000
Recovery relating to cost overruns on a large project												5,100,000
Revenues		674,772,000	717,194,000	562,397,000	405,114,000	412,756,000	378,865,000					3,800,000			635,253,000	686,581,000	533,339,000
Other assets		7,333,000	6,507,000									1,300,000
Proceeds from legal settlements	$ 1,700,000													$ 1,700,000
Concentration risk percentage					60.00%	58.00%	67.00%	17.00%	13.00%	16.00%	11.00%