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New Accounting Standards (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Income Tax Expense (Benefit) | $ 80.9 | $ 54.4 | $ 26.3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) | 7.3 |  |
Operating Leases, Future Minimum Payments Due | 79.1 |  |
Accounting Standards Update 2016-09 [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Income Tax Expense (Benefit) | (33.1) |  |
Excess Tax Benefit from Share-based Compensation, Operating Activities | 33.1 |  |
Accounting Standards Update 2017-07 [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Defined Benefit Plan, Service Cost | 10.4 |  |
Accounting Standards Update 2016-02 [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Operating Leases, Future Minimum Payments Due | 79.1 |  |
Accounting Standards Update 2016-16 [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
New Accounting Pronouncement, Cumulative Effect of Change on Equity | $ 4.1 |  |

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