Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 5.8		$ 67.9
Effective Income Tax Rate Reconciliation, Transition tax, Net of Foreign Taxes Deemed Paid, Amount		$ 3.3	$ 11.0
Second component of tax deductible goodwill, net of tax		1.3
Liability for Uncertain Tax Positions, Noncurrent		23.2
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense		6.1
Deferred tax asset, Uncertain tax position		6.0
Unrecognized Tax Benefits, Interest on Income Taxes Expense		1.3
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign		24.1
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 15.6	(24.1)
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		552.2
Deferred Tax Assets, Tax Credit Carryforwards		25.8
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		(4.6)
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		124.6
Deferred Tax Assets, Tax Credit Carryforwards		67.1
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		$ (62.5)