Summary of Significant Accounting Polices - Foreign Currency Transactions and Translation (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Foreign Currency Transactions and Translations
Total transaction gains (losses) related primarily to advances to and between foreign subsidiaries	$ 0.7	$ (2.2)	$ 0.7

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 45
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-URI http://asc.fasb.org/extlink&oid=109240200&loc=d3e30690-110894

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