Significant Accounting Policies - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Prepaid expense current	$ 43.9	$ 36.1
Contract assets	14.8	0.0
Other assets current	8.6	8.5
Prepaid Expense and Other Assets, Current	$ 67.3	$ 44.6

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as current.

+ References

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-Publisher FASB
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Amount of current assets classified as other.

+ References

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Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Subparagraph (SX 210.5-02(8))
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Amount of asset related to consideration paid in advance for costs that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

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