Basis of Presentation and Responsibility for Interim Financial Statements - Adoption of New Accounting Standards (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
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Liability, Current	$ 19.8		$ 19.8		$ 0.0
Operating Lease, Liability, Noncurrent	62.1		62.1		0.0
Net periodic benefit cost	(10.5)	$ 1.8	(8.8)	$ 3.6
Operating Lease, Right-of-Use Asset	$ 78.7		$ 78.7		$ 0.0