Quarterly report pursuant to Section 13 or 15(d)

Derivative Contracts - Summary of Outstanding Commodity Derivative Contracts (Detail)

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Derivative Contracts - Summary of Outstanding Commodity Derivative Contracts (Detail) - USD ($)
$ in Millions
Sep. 30, 2018
Dec. 31, 2017
Derivatives, Fair Value [Line Items]    
Net Notional Amount $ 153.9 $ 16.6
Forward Contracts [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 3.9 16.6
Forward Contracts [Member] | Notional Amount - Long [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 42.4 46.1
Forward Contracts [Member] | Notional Amount - Short [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 38.5 29.5
Interest Rate Swap [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 150.0 0.0
Metal [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 1.5 12.8
Energy and utilities [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount $ 2.4 $ 3.8