Acquisitions and Divestitures (Details Textual) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2015 USD ($) facility	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain recognized		$ 0.0	$ 0.0	$ 8.2	$ 0.0
Texas, Mississippi, and Louisiana | Galvanizing business | Construction Products Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of facilities disposed | facility	6
Gain recognized	$ 8.2