Derivative Financial Instruments - Fair Values of Outstanding Zero Cost Collar and Forward Contracts Recorded as Assets and Liabilities (Detail) - Zero Cost Collars [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Asset Derivatives:
Other current assets	$ 262	$ 1,456
Liability Derivatives:
Other current liabilities	33
Other Current Assets [Member]
Asset Derivatives:
Other current assets	262	$ 1,456
Other Current Liabilities [Member]
Liability Derivatives:
Other current liabilities	$ 33