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Supplemental Financial Statement Information - Other Non-operating Income (Expense) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Other Nonoperating Income (Expense) [Abstract] |  |  |
Rent and royalty income | $ 3.5 | $ 1.4 | $ 2.0
Net gains on property and investments | 0.5 | 1.0 | 0.0
Other | 0.0 | 0.0 | (0.4)
Other income, net | $ 4.0 | $ 2.4 | $ 1.6

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- Definition Rent, Royalty, and Other Income + References No definition available. + Details
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- Definition Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2443-110228 + Details
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- Definition Amount of income (expense) related to nonoperating activities, classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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