Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Research and Development		$ 26.6	$ 24.6
Income before income taxes:
Domestic		79.2	82.2	$ 28.3
Foreign		104.3	162.7	182.6
Income (loss) before income taxes		183.5	244.9	210.9
Provision for income taxes:
Federal-current		(6.3)	(4.9)	0.0
Federal-deferred		(19.8)	(29.3)	(144.6)
State and local-current		(0.5)	1.6	0.2
State and local - deferred		(5.8)	(3.5)	(1.7)
Foreign-current		(42.4)	(49.9)	(50.8)
Foreign-deferred		18.0	7.9	(3.6)
(Provision for) benefit from income taxes		$ (56.8)	(78.1)	(200.5)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%
Income tax provision analysis
Tax provision at U.S. federal income tax rate		$ (38.5)	(51.4)	(73.8)
Effective Income Tax Rate Reconciliation, U.S. taxes on foreign earnings		16.7	30.9	1.2
Effective Income Tax Rate Reconciliation, Tax Reform, Amount	$ 143.0	0.0	(17.1)	143.0
Change in provision resulting from:
Decrease (increase) in valuation allowance		(4.2)	(6.3)	(0.3)
Research and development credit		3.4	9.4	5.1
State and local income taxes, net		(3.4)	(1.9)	(1.8)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount		3.0	(0.7)	6.4
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount		(2.9)	(11.3)	13.3
Nontaxable income/non-deductible expenses		(2.5)	(1.6)	(2.6)
Effective Income Tax Rate Reconciliation, Unrecognized tax benefit accrual/releases		(2.3)	(5.7)	0.0
Stock-based compensation		(1.7)	(3.4)	2.7
Effective Income Tax Rate Reconciliation, Tax Reform, Amount	$ (143.0)	0.0	17.1	(143.0)
Other		4.4	(2.8)	(5.3)
(Provision for) benefit from income taxes		$ (56.8)	(78.1)	(200.5)
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			120.1
Income tax expense, repatriation of foreign earnings			(9.5)	37.4
Income tax expense, state and foreign taxes on unremitted earnings			$ 2.7	$ (4.9)