Gross Amounts of Recognized Assets and Liabilities (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Fair Value of Derivatives, Asset
Derivative assets as classified in the unaudited condensed consolidated balance sheet	$ 0.8	$ 0.2
Derivative assets, effect of counterparty netting arrangements		(0.2)
Net derivatives assets (liabilities) as classified in the consolidated balance sheets	0.8
Fair Value of Derivatives, Liability
Derivative liabilities as classified in the unaudited condensed consolidated balance sheet		(0.9)
Derivative liabilities, effect of counterparty netting arrangements		0.2
Net derivatives assets (liabilities) as classified in the consolidated balance sheets		(0.7)
Metal
Fair Value of Derivatives, Asset
Derivative assets as classified in the unaudited condensed consolidated balance sheet	0.3	0.2
Fair Value of Derivatives, Liability
Derivative liabilities as classified in the unaudited condensed consolidated balance sheet		(0.3)
Natural Gas
Fair Value of Derivatives, Asset
Derivative assets as classified in the unaudited condensed consolidated balance sheet	$ 0.5
Fair Value of Derivatives, Liability
Derivative liabilities as classified in the unaudited condensed consolidated balance sheet		$ (0.6)

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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