Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of the total gross unrecognized tax benefits
Balance, January 1	$ 92.0	$ 91.1	$ 127.3
Additions based on tax positions related to current year	24.1	16.8	16.1
Unrecognized tax benefits, decrease resulting from prior period tax positions		(2.4)
Unrecognized tax benefits, increase resulting from prior period tax positions	17.7		1.6
Reductions for closure of tax audits and settlements	(7.7)	(19.9)	(45.7)
Reductions for lapse in statute of limitations	0.0	(0.8)	(5.0)
Unrecognized tax benefits, increase resulting from foreign currency translation	5.7	7.2
Unrecognized tax benefits, decrease resulting from foreign currency translation			(3.2)
Balance, December 31	120.4	92.0	$ 91.1
Income tax penalties and interest expense	10.4	6.4
Unrecognized tax benefits that would impact effective tax rate	111.6
Income tax penalties and interest accrued on unrecognized tax benefits	31.5	$ 22.6
Other Current Liabilities [Member]
Reconciliation of the total gross unrecognized tax benefits
Balance, December 31	$ 9.7

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of unrecognized tax benefits.

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Amount of decrease in unrecognized tax benefits resulting from foreign currency translation.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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