Segment Reporting (Revenue by Geographical Areas) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues from External Customers [Line Items]
Revenues	$ 936.8	$ 972.3	$ 1,927.3	$ 1,896.0
Revenue as Percentage of Consolidated Revenue	100.00%	100.00%	100.00%	100.00%
Domestic
Revenues from External Customers [Line Items]
Revenues	$ 897.9	$ 929.8	$ 1,843.3	$ 1,810.9
Revenue as Percentage of Consolidated Revenue	95.80%	95.60%	95.60%	95.50%
Foreign
Revenues from External Customers [Line Items]
Revenues	$ 38.9	$ 42.5	$ 84.0	$ 85.1
Revenue as Percentage of Consolidated Revenue	4.20%	4.40%	4.40%	4.50%