Acquisitions and Divestitures (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Divestitures:
Proceeds		$ 0.0	$ 51.3	$ 0.0
Gain recognized		0.0		0.0
Goodwill charged off		0.0	17.3	0.0
Acquisitions:
Purchase price		0.0	46.2	720.9
Net cash paid		0.0	46.2	714.4
Goodwill recorded		0.0	0.0	495.0
Construction Products Group
Acquisitions:
Purchase price		$ 0.0	46.2	$ 6.1
Construction Products Group \| Texas, Mississippi, and Louisiana \| Galvanizing Business
Divestitures:
Gain recognized	$ 8.3		$ 8.3

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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