Fair Value Measurements - Fair Value, Balance Sheet Grouping (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financial Assets
Commodity derivatives	$ 51,580	$ 3,916
Financial Liabilities
Commodity derivatives	601	5,082
Total
Financial Assets
Deferred compensation plan	1,220	2,033
Commodity derivatives	58,048	8,890
Financial Liabilities
Commodity derivatives	7,069	10,056
Level 1
Financial Assets
Deferred compensation plan	1,220	2,033
Commodity derivatives	0	0
Financial Liabilities
Commodity derivatives	0	0
Level 2
Financial Assets
Deferred compensation plan	0	0
Commodity derivatives	58,048	8,890
Financial Liabilities
Commodity derivatives	7,069	10,056
Level 3
Financial Assets
Deferred compensation plan	0	0
Commodity derivatives	0	0
Financial Liabilities
Commodity derivatives	$ 0	$ 0