Income Taxes - (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net deferred tax liabilities		$ 225.4	$ 201.7
Basis differences in investments outside the U.S.		$ 220.0
Statutory federal income tax rate	21.00%	21.00%	21.00%	35.00%
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Transition Tax on Accumulated Foreign Earnings, Percent			0.155
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent			0.08
TCJA, effect on income tax expense, transition tax				$ 36.0
TCJA, effect on income tax expense, remeasured deferred tax assets and liabilities				$ 73.0
Effective tax rate		21.00%	23.40%	22.10%
Net discrete tax charges (as a percent)		2.40%	0.60%	9.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent		(2.30%)	(1.10%)	(1.30%)
Employee service share-based compensation, tax benefit from exercise of stock options		$ 8.0	$ 5.0	$ 8.0
Excess tax benefit from share-based compensation, operating activities		6.0	3.0	5.0
Net operating loss carryforwards		152.0
Operating loss carryforwards, valuation allowances		119.0
Gross unrecognized tax benefits	$ 37.4	9.1	27.2	37.4	$ 49.2
Recognized potential interest and penalties		1.0	1.0	$ 3.0
Unrecognized tax benefits that would impact effective tax rate		11.0
Estimated reduction in unrecognized tax benefits within twelve months		2.0
Continuing operations
Gross unrecognized tax benefits		9.0	27.0
Unrecognized tax benefits, net of offsetting indirect tax benefits		11.0	26.0
Unrecognized tax benefits, indirect tax benefits		18.0	6.0
Potential interest and penalties		2.0	(5.0)
United States | Entity
Net deferred tax liabilities		148.0	149.0
Foreign tax | Entity
Net deferred tax liabilities		$ 77.0	$ 53.0