Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments, Fair Value, Hedging Activities, and Concentrations of Credit Risk - Additional Information (Detail)

v3.19.3
Financial Instruments, Fair Value, Hedging Activities, and Concentrations of Credit Risk - Additional Information (Detail) - USD ($)
$ in Millions
Sep. 30, 2019
Dec. 31, 2018
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Fair value of financing leases $ 15.8 $ 15.8
Financing lease obligations 18.7 $ 18.5
Commodity Contracts [Member]    
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Commodity derivative assets, notional amount $ 5.1