Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Derivative Contracts - Summary of Outstanding Commodity Derivative Contracts (Detail) - USD ($)
$ in Millions
Dec. 31, 2018
Dec. 31, 2017
Derivatives, Fair Value [Line Items]    
Net Notional Amount $ 180.9 $ 16.6
Interest Rate Swap [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 150.0 0.0
Commodity Contract [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 27.9 12.8
Energy Related Derivative [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 3.0 3.8
Forward Contracts [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 30.9 16.6
Forward Contracts [Member] | Notional Amount - Long [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount 67.4 46.1
Forward Contracts [Member] | Notional Amount - Short [Member]    
Derivatives, Fair Value [Line Items]    
Net Notional Amount $ 36.5 $ 29.5