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Goodwill and Intangible Assets - Narrative (Details) - USD ($) |  | 6 Months Ended |
--- | --- | --- | ---
Jul. 02, 2018 | Mar. 31, 2019 | Sep. 30, 2018
Goodwill [Line Items] |  |  |
Impairment of goodwill | $ 0 |  |
Estimated fair values that exceeded their carrying values, percent (more than) | 30.00% |  |
Income approach, discounted cash flow method |  |  |
Goodwill [Line Items] |  |  |
Weighted rate used in fair value of goodwill (as a percent) |  | 70.00% |
Market approach |  |  |
Goodwill [Line Items] |  |  |
Weighted rate used in fair value of goodwill (as a percent) |  | 30.00% |
GSG |  |  |
Goodwill [Line Items] |  |  |
Gross amounts of goodwill |  | $ 444,400,000 | $ 407,400,000
Accumulated impairment |  |  | 17,700,000
CIG |  |  |
Goodwill [Line Items] |  |  |
Gross amounts of goodwill |  | 498,900,000 | 507,000,000
Accumulated impairment |  | $ 97,900,000 | $ 97,900,000

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- Definition Amount before 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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
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