Revenues, Unbilled Revenue and Deferred Revenue (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Contracts with Customers, Assets and Liabilities [Abstract]
Unbilled revenue	$ 160.9	$ 13.3
Deferred revenue	310.5	$ 291.2
Other Current Assets [Member]
Contracts with Customers, Assets and Liabilities [Abstract]
Unbilled revenue (current amount)	160.9
Other Current Liabilities [Member]
Contracts with Customers, Assets and Liabilities [Abstract]
Deferred revenue (current amount)	111.7
Other Liabilities [Member]
Contracts with Customers, Assets and Liabilities [Abstract]
Deferred revenue (noncurrent)	$ 198.8