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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 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 + Details
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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 + Details
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