Acquisitions Acquisitions (Details) - USD ($) $ in Millions	Dec. 31, 2017	Jan. 26, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 886.8		$ 774.7	$ 778.3
Axtone Railway Components Acquisition [Member]
Business Acquisition [Line Items]
Cash		$ 9.4
Receivables		11.5
Inventory		13.6
Plant, property and equipment		13.1
Goodwill		83.0
Other intangible assets		9.9
Other assets		6.0
Accounts payable and accrued liabilities		(14.9)
Postretirement liabilities		(4.2)
Other liabilities		(4.3)
Net assets acquired		$ 123.1