Background and Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Plan [Member] | Other Nonoperating Income (Expense) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic pension expense	$ 0.2	$ 0.3	$ 0.5	$ 0.6