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Income Taxes Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Liability for unrecognized tax benefit	$ 27.6	$ 26.1
Items generating unrecognized tax benefits	25.1	23.7
Interest and related penalties	$ 2.5	$ 2.4
Earliest Tax Year
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Tax year subject to examination by major tax jurisdictions	2013
Latest Tax Year
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Tax year subject to examination by major tax jurisdictions	2017

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- Definition

Unrecognized Tax Benefits, Current Year Tax Positions

+ References

No definition available.

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- Definition

Tax year that remains open to examination under enacted tax laws, in CCYY format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

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Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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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