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Commitments and Contingencies (Narrative) (Details) - USD ($) | 12 Months Ended
--- | ---
Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2014
Guarantee Obligations [Line Items] |  |  |
Lease expense for operating leases | $ 3,500,000 | $ 4,000,000 | $ 3,900,000
Additional bonding capacity | 516,400,000 |  |
Liquidated damages | 2,500,000 |  |
Probable liquidated damages | 1,500,000 |  |
Loss contingency, estimate of actual or projected loss | 1,500,000 |  |
Facility Agreement | Powell (UK) Limited |  |  |
Guarantee Obligations [Line Items] |  |  |
Guarantee liability | 4,100,000 |  |
Revolving credit facility | 9,100,000 |  |
Amount of credit facility remaining borrowing capacity | 5,000,000 |  |
Financial Standby Letter of Credit |  |  |
Guarantee Obligations [Line Items] |  |  |
Guarantee liability | 26,800,000 |  |
Performance Guarantee |  |  |
Guarantee Obligations [Line Items] |  |  |
Guarantee liability | $ 233,600,000 |  |

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- Definition The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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