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Pension Benefit Obligations - Multiemployer (Details) - Multiemployer Pension Plans $ in Millions | 12 Months Ended
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Sep. 30, 2018 USD ($) plan | Sep. 30, 2017 USD ($)
Multiemployer Pension Plans |  |
Number of minimum construction-industry pension plans participated | plan | 200 |
Aggregate contributions to plans | $ | $ 49.8 | $ 48.8

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- Definition Represents the number of multiemployer pension plans participated as on date. + References No definition available. + Details
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- Definition Amount of contributions made to multiemployer plan by employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450691-114947 + Details
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- Details
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