Retirement Benefits - Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
Mar. 31, 2019 |
Mar. 31, 2018 |
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| Defined Benefit Plan Disclosure [Line Items] | ||||
| Defined Contribution Plan, Cost | $ 2.9 | $ 2.9 | $ 5.7 | $ 5.6 |
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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| X | ||||||||||
- Definition Amount of cost for defined contribution plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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