Revenues, Unbilled Revenue and Deferred Revenue (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Contracts with Customers, Assets and Liabilities [Abstract]
Unbilled revenue	$ 13.3	$ 0.0
Deferred revenue	291.2	$ 224.7
Other Current Assets [Member]
Contracts with Customers, Assets and Liabilities [Abstract]
Unbilled revenue (current amount)	13.3
Other Current Liabilities [Member]
Contracts with Customers, Assets and Liabilities [Abstract]
Deferred revenue (current amount)	80.9
Other Liabilities [Member]
Contracts with Customers, Assets and Liabilities [Abstract]
Deferred revenue (noncurrent)	$ 210.3

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Amount, before 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.

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