Basis of Presentation and Responsibility for Interim Financial Statements - Adoption of New Accounting Standards (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Liability, Current	$ 19.8		$ 19.8		$ 0.0
Operating Lease, Liability, Noncurrent	63.0		63.0		0.0
Net periodic benefit cost	1.8	$ 4.0	(7.3)	$ 7.6
Operating Lease, Right-of-Use Asset	$ 80.0		$ 80.0		$ 0.0