Income Taxes - Unrecognized Tax Benefits (Details) $ in Millions	Sep. 30, 2018 USD ($)
Income Taxes
Unrecognized tax benefits, if recognized, would affect effective tax rate	$ 30.1
Accrued gross interest and penalties	$ 1.8

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant