Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	$ 9.7	$ (58.4)	$ 18.5	$ (46.6)
Income tax expense as a percent of pre-tax income (loss)	21.50%	(173.30%)	21.60%	(67.60%)
Tax benefit due to changes in prior year tax positions	$ 1.8		$ 1.8
Tax Cuts and Jobs Act of 2017, income tax benefit		$ 66.0		$ 66.0
Tax Cuts and Jobs Act of 2017, provisional net benefit for re-measurement of deferred tax assets and liabilities		73.3		73.3	$ 74.6
Tax Cuts and Jobs Act of 2017, provisional tax expense for transition tax		5.1		$ 5.1	5.0
Tax Cuts and Jobs Act of 2017, tax expense (benefit) for transition tax	0.2				(4.7)
Discrete tax charge due to re-measurement of deferred tax assets and liabilities	$ 0.2
Indefinitely reinvested foreign earnings					$ 100.6
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)		$ 2.2