Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	23.00%	23.00%	19.00%	22.00%
income tax benefit related to tax act			$ 12.6
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	$ 7.2	$ 8.2
Statutory federal rate	21.00%	35.00%
Tax Credit Carryforward, Amount					$ 67.9
Foreign Earnings Repatriated			1,150.0
Deferred Tax Liabilities, Undistributed Foreign Earnings			60.7
Deferred Tax Liabilities, Gross, Noncurrent	$ 81.0		81.0
Liabilities, Other than Long-term Debt, Noncurrent	4.8		4.8
Income Taxes Paid	10.6
Deferred Tax Liabilities, Financing Arrangements	$ 439.2		$ 439.2