Income Taxes - Gross Unrecognized Tax Positions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1,	$ 8.4	$ 6.4	$ 3.8
Additions based on tax positions related to the current year	2.0	2.1	2.7
Decreases due to lapse of applicable statute of limitations	(0.9)	(0.1)	(0.1)
Settlements	0.0	0.0	0.0
Balance as of December 31,	$ 9.5	$ 8.4	$ 6.4

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

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

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- Definition

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

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- Definition

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

+ References

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

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