Commitments and Contingencies (Narrative) (Details)	3 Months Ended
	Dec. 31, 2015 USD ($)
Guarantee Obligations [Line Items]
Additional bonding capacity	$ 442,500,000
Liquidated damages	7,500,000
Probable liquidated damages	2,200,000
Loss contingency, estimate of actual or projected loss	1,700,000
Facility Agreement | Powell (UK) Limited
Guarantee Obligations [Line Items]
Guarantee liability	3,000,000
Revolving credit facility	14,800,000
Amount of credit facility remaining borrowing capacity	11,800,000
Financial Standby Letter of Credit
Guarantee Obligations [Line Items]
Guarantee liability	21,600,000
Performance Guarantee
Guarantee Obligations [Line Items]
Guarantee liability	$ 307,500,000