Business Segments Revenues by Geographic Location (Details) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	[1]	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,025.2	$ 1,002.7	$ 972.3	$ 923.7	$ 929.7	$ 906.4	$ 878.5		$ 685.2	$ 3,923.9	$ 3,399.8	$ 2,626.0
Domestic [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues										3,749.2	3,241.8	2,494.5
Foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues										$ 174.7	$ 158.0	$ 131.5

[1] ECS was acquired on April 2, 2018, see Note 4 – Acquisitions.