Supplementary Financial Statement Information Intangibles (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross Amount	$ 59.6		$ 59.6		$ 55.9
Intangible Assets, Accumulated Amortization	(16.2)		(16.2)		(12.0)
Intangible Assets, Net Amount	43.4		43.4		43.9
Amortization of Intangible Assets	2.2	$ 2.3	4.2	$ 4.7
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross Amount	36.6		36.6		36.6
Intangible Assets, Accumulated Amortization	(10.0)		(10.0)		(7.4)
Intangible Assets, Net Amount	26.6		26.6		29.2
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross Amount	23.0		23.0		19.3
Intangible Assets, Accumulated Amortization	(6.2)		(6.2)		(4.6)
Intangible Assets, Net Amount	$ 16.8		$ 16.8		$ 14.7