Revenue Recognition, Contracts with Customers - Contracts with Customer Asset and Liability (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract assets	$ 0.0	$ 0.0
Contract liabilities	$ 6.3	$ 5.5
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract assets			$ 0.0
Contract liabilities			$ 3.1