Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax Credit Carryforward [Line Items]
Tax Cuts and Jobs Act, provisional income tax expense (benefit)	$ 56.5		$ 6.0
Income tax credits	21.0	$ 24.5	21.0
Net operating loss carryforwards	19.0	22.2	19.0
Valuation allowance	19.4	21.8	19.4
Undistributed earnings of foreign subsidiaries		220.0
Income taxes paid		106.3	130.8	$ 117.4
Unrecognized tax benefits timing of deductibility unknown		4.9
Unrecognized tax benefits, income tax penalties and interest expense		1.8	0.5	$ 0.7
Unrecognized tax benefits, income tax penalties and interest accrued	$ 5.2	7.0	$ 5.2
Minimum
Tax Credit Carryforward [Line Items]
Unrecognized tax benefits that would impact effective tax rate		30.7
Significant (increase) decrease in unrecognized tax benefits is reasonably possible, estimated range of change, upper bound		5.5
Maximum
Tax Credit Carryforward [Line Items]
Significant (increase) decrease in unrecognized tax benefits is reasonably possible, estimated range of change, upper bound		6.5
Federal, State, and Local
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards		22.2
Tax credit carryforward indefinitely
Tax Credit Carryforward [Line Items]
Income tax credits		14.1
Net operating loss carryforwards		7.9
Carryforward Subject To Expiration
Tax Credit Carryforward [Line Items]
Income tax credits		10.4
Net operating loss carryforwards		$ 14.3