Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Other Tax Expense (Benefit) [Line Items]
Effective income tax rate	21.50%	14.30%	20.10%	17.60%
Federal statutory income tax rate			21.00%	35.00%
Excess tax benefits	$ (1.9)		$ 5.4	$ 6.9
Discrete tax benefit related to TCJA	(1.7)		4.8
Release of valuation allowances	1.2		7.3	10.8
Provisional tax expense related to transition tax on foreign earnings					$ 429.2
Provisional tax benefit related to remeasurement of deferred tax balances					$ 62.3
Discrete tax benefit related to one-time transition tax			2.8
Discrete tax benefit related to other provisions of TCJA			2.0
Income tax expense on global intangible low-taxed income	1.1		7.2
Foreign accrual to return adjustment
Other Tax Expense (Benefit) [Line Items]
Other tax expense (benefit)	$ (2.0)		(2.0)
Gain on sale of business
Other Tax Expense (Benefit) [Line Items]
Other tax expense (benefit)			42.0
Tax accounting method change
Other Tax Expense (Benefit) [Line Items]
Other tax expense (benefit)			$ (8.0)
Foreign rate changes
Other Tax Expense (Benefit) [Line Items]
Other tax expense (benefit)				14.8
Out-of-period adjustments
Other Tax Expense (Benefit) [Line Items]
Other tax expense (benefit)				$ 5.1