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Income Taxes - Changes in Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of beginning and ending amount of unrecognized tax benefits
Balance, beginning of period	$ 32.4	$ 26.8	$ 26.9
Additions based on current year tax positions	2.4	6.0	3.8
Additions based on prior years’ tax positions	8.4	1.5	0.6
Reduction for prior years’ tax positions	(2.0)	0.0	0.0
Reductions related to lapses of statutes of limitations	(6.3)	(2.3)	(4.7)
Settlements	(1.3)	0.0	0.0
Additions (reductions) related to foreign exchange rates	(0.5)	0.4	0.2
Balance, end of period	$ 33.1	$ 32.4	$ 26.8

X

- Definition

The gross amount of additions (reductions) related to foreign exchange rates resulting from settlements with taxing authorities.

+ References

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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 tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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