Income Tax (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate (benefit)	227.70%	(28.50%)	(80.20%)	(87.30%)
Income Tax [Line Items]
Tax Cuts And Jobs Act Of 2017, transition tax for accumulated foreign earnings			$ 443.2
Tax Cuts And Jobs Act Of 2017, provisional income tax expense (benefit), effect of change on earnings per share, diluted			$ (1.79)
Tax Cuts And Jobs Act Of 2017, provisional income tax expense (benefit)			$ 627.7
Tax Cuts And Jobs Act Of 2017,change in tax rate, deferred tax liability, provisional income tax expense			(5.5)
Tax Cuts And Jobs Act Of 2017, transition tax for accumulated foreign earnings			622.2
Tax Cuts And Jobs Act Of 2017, change in tax rate, deferred tax asset			142.6
Tax Cuts And Jobs Act Of 2017, provisional income tax expense (benefit), deferred tax assets, tax credit carryforwards, foreign			$ (36.4)
Scenario, Forecast
Income Tax [Line Items]
Effective income tax rate reconciliation, at Federal statutory income tax rate					31.50%