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Business Acquisitions, Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands | 12 Months Ended
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Sep. 30, 2016 | Sep. 30, 2015
Goodwill |  |
Maximum period to determine final value of identifiable intangible assets | 12 months |
Changes in the carrying value of goodwill by reporting segment |  |
Goodwill at the beginning of the period | $ 5,820,692 | $ 1,937,300
Post-Acquisition Adjustments | 39,400 | 6,100
Foreign Exchange Impact | (25,000) | (168,100)
Disposed | (11,300) |
Acquired |  | 4,045,400
Goodwill at the end of the period | 5,823,843 | 5,820,692
Design and Consulting Services |  |
Changes in the carrying value of goodwill by reporting segment |  |
Goodwill at the beginning of the period | 3,163,300 | 1,479,200
Post-Acquisition Adjustments | 26,700 | 5,500
Foreign Exchange Impact | 8,200 | (96,000)
Acquired |  | 1,774,600
Goodwill at the end of the period | 3,198,200 | 3,163,300
Construction Services |  |
Changes in the carrying value of goodwill by reporting segment |  |
Goodwill at the beginning of the period | 918,500 | 276,900
Post-Acquisition Adjustments | 8,700 | 600
Foreign Exchange Impact | (700) | (34,000)
Disposed | (11,300) |
Acquired |  | 675,000
Goodwill at the end of the period | 915,200 | 918,500
Management Services |  |
Changes in the carrying value of goodwill by reporting segment |  |
Goodwill at the beginning of the period | 1,738,900 | 181,200
Post-Acquisition Adjustments | 4,000 |
Foreign Exchange Impact | (32,500) | (38,100)
Acquired |  | 1,595,800
Goodwill at the end of the period | $ 1,710,400 | $ 1,738,900

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- Definition Maximum period from the date of acquisition to determine the final value of the identifiable intangible assets in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 + Details
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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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- Definition Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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- Definition Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e961-128460 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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- Definition Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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