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Goodwill - Goodwill by Segment (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Sep. 30, 2019
--- | --- | ---
Goodwill [Line Items] |  |
Goodwill | $ 55.5 | $ 51.2
Commercial Hedging |  |
Goodwill [Line Items] |  |
Goodwill | 30.3 | 30.3
Global Payments |  |
Goodwill [Line Items] |  |
Goodwill | 7.6 | 7.6
Physical Commodities |  |
Goodwill [Line Items] |  |
Goodwill | 4.6 | 4.6
Securities |  |
Goodwill [Line Items] |  |
Goodwill | 8.7 | 8.7
Clearing and Execution Services Segment |  |
Goodwill [Line Items] |  |
Goodwill | $ 4.3 | $ 0.0

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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
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