New Accounting Standards (Details) - USD ($) $ in Millions	12 Months Ended
	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