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	Dec. 31, 2015
Tax Credit Carryforward [Line Items]
One-time tax reserves		$ 98.7
Net benefit related to U.S. Tax Reform	$ 29.9		$ 29.9
Valuation allowance release related to U.S Tax Reform			33.5
Uncertain tax position related to U.S Tax Reform			3.6
Write-off of deferred tax asset related to U.S. Tax Reform			161.4
Reversal of deferred tax liability related to unremitted earnings due to U.S. Tax Reform			66.7
Establishment of deferred tax assets for other miscellaneous withholding tax items due to U.S. Tax Reform			5.5
One-time tax on offshore earnings due to U.S. Tax Reform			2.9
Net increase (decrease) in valuation allowance		45.6
Deferred tax assets, tax credit carryforwards, excluding adoption of ASU 2013-11		842.5
Tax credit carryforwards	981.0	830.5	981.0
Tax credit carryforward, valuation allowance		812.5
Foreign tax credit carryforwards		793.8
Minimum tax credit carryforwards		18.0
Tax credit carryforwards, research		21.0
Deferred tax assets, net operating loss		2,166.2
Operating loss carryforwards, valuation allowance		2,073.3
Operating loss carryforwards, foreign		2,045.5
Change in deferred tax liability associated with undistributed earnings		(5.1)
Deferred tax liabilities, undistributed foreign earnings		17.5
Undistributed earnings of foreign subsidiaries		1,100.0
Total gross unrecognized tax benefits	48.6	137.6	48.6	$ 58.7	$ 53.0
Unrecognized tax benefits that would impact effective tax rate		123.2
Expense for interest and penalties		1.3	0.0	$ 2.5
Accrued interest and penalties	9.9	7.4	$ 9.9
Foreign
Tax Credit Carryforward [Line Items]
Operating loss carryforwards, valuation allowance		1,974.5
State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Operating loss carryforwards, valuation allowance		98.8
Deferred tax assets, state tax loss carryforwards		98.8
Operating loss carryforwards		1,396.7
Europe, Middle East & Africa
Tax Credit Carryforward [Line Items]
Net increase (decrease) in valuation allowance	$ 25.5
Foreign
Tax Credit Carryforward [Line Items]
Operating loss carryforwards		8,616.2
Operating loss carryforwards, not subject to expiration		6,927.5
Operating loss carryforwards, subject to expiration		1,688.7
Investment Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforward		9.7
Deferred Tax Asset Generated In Current Year
Tax Credit Carryforward [Line Items]
Net increase (decrease) in valuation allowance		138.6
Deferred Tax Assets Expensed Or Written Off In Current Year
Tax Credit Carryforward [Line Items]
Net increase (decrease) in valuation allowance		(93.0)
Excess Tax Basis Reallocated
Tax Credit Carryforward [Line Items]
Net increase (decrease) in valuation allowance		(57.2)
State Deferred Tax Assets
Tax Credit Carryforward [Line Items]
Net increase (decrease) in valuation allowance		(15.3)
Other Deferred Tax Assets
Tax Credit Carryforward [Line Items]
Net increase (decrease) in valuation allowance		(11.7)
Deferred Tax Assets Associated With Repatriation Of Earnings
Tax Credit Carryforward [Line Items]
Net increase (decrease) in valuation allowance		$ (8.8)