Accounts Receivable and Major Customers - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020 USD ($) Customer	Dec. 31, 2019 USD ($) Customer	Jan. 01, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customers	$ 39,672,000	$ 63,165,000
Retained earnings	9,354,000	319,987,000
Accounts Receivable, Allowance for Credit Loss	197,000	52,000
Accounts Receivable, Credit Loss Expense (Reversal)	69,000
Accounts Receivable, Allowance for Credit Loss, Writeoff	$ 0
Name of Major Customer [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commodity Products, Number of Customers | Customer	20
Financing Receivable, Credit Risk Percentage	0.00%
Accounts Receivable, Allowance for Credit Loss	$ 0	0
Accounts Receivable, Credit Loss Expense (Reversal)	0
Accounts Receivable, Allowance for Credit Loss, Writeoff	$ 0
Joint Interest Partners, Mutual Operators [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commodity Products, Number of Customers | Customer	2
Financing Receivable, Credit Risk Percentage	5.00%		0.00%
Accounts Receivable, Allowance for Credit Loss	$ 9,000	0
Accounts Receivable, Credit Loss Expense (Reversal)	9,000
Accounts Receivable, Allowance for Credit Loss, Writeoff	$ 0
Joint Interest Partners, Large Partners [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commodity Products, Number of Customers | Customer	3
Financing Receivable, Credit Risk Percentage			1.00%
Accounts Receivable, Allowance for Credit Loss	$ 87,000	0
Accounts Receivable, Credit Loss Expense (Reversal)	27,000
Accounts Receivable, Allowance for Credit Loss, Writeoff	$ 0
Joint Interest Partners, All Others [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commodity Products, Number of Customers | Customer	20
Financing Receivable, Credit Risk Percentage	10.00%		5.00%
Financing Receivable, Past Due	$ 200,000
Accounts Receivable, Allowance for Credit Loss	101,000	$ 52,000
Accounts Receivable, Credit Loss Expense (Reversal)	33,000
Accounts Receivable, Allowance for Credit Loss, Writeoff	0
Cumulative Effect, Period of Adoption, Adjustment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Allowance for Credit Loss			$ 76,000
Cumulative Effect, Period of Adoption, Adjustment [Member] | Name of Major Customer [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Allowance for Credit Loss			0
Cumulative Effect, Period of Adoption, Adjustment [Member] | Joint Interest Partners, Mutual Operators [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Allowance for Credit Loss			0
Cumulative Effect, Period of Adoption, Adjustment [Member] | Joint Interest Partners, Large Partners [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Allowance for Credit Loss			60,000
Cumulative Effect, Period of Adoption, Adjustment [Member] | Joint Interest Partners, All Others [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Allowance for Credit Loss			$ 16,000
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained earnings	$ 100,000
Accounts Receivable | Customer Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of major customers | Customer	3	4
Revenues, major customers	$ 150,800,000	$ 354,600,000
Concentration risk, percentage	56.00%	76.00%
Accounts Receivable | Customer Concentration Risk | Major Customer 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 72,300,000	$ 172,300,000
Concentration risk, percentage	27.00%	37.00%
Accounts Receivable | Customer Concentration Risk | Major Customer 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 50,200,000	$ 84,600,000
Concentration risk, percentage	19.00%	18.00%
Accounts Receivable | Customer Concentration Risk | Major Customer 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 28,300,000	$ 50,700,000
Concentration risk, percentage	10.00%	11.00%
Accounts Receivable | Customer Concentration Risk | Major Customer Four [Domain]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers		$ 47,000,000.0
Concentration risk, percentage		10.00%
Accounts Receivable | Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage	47.00%	70.00%
Accounts receivable, major customers	$ 18,600,000	$ 44,500,000