Accounts Receivable and Revenues from Contracts with Customers - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Customer	Jun. 30, 2017 USD ($) Customer	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic	$ (2,521)	$ 21,329	$ 7,774	$ 49,410
Document Period End Date			Jun. 30, 2018
Sales Revenue | Customer Concentration Risk [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of major customers | Customer			3	1
Revenues, major customers			$ 157,800	$ 64,600
Concentration risk, percentage			84.00%	91.00%
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers			$ 81,000
Concentration risk, percentage			43.00%
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers			$ 41,000
Concentration risk, percentage			22.00%
Sales Revenue | Customer Concentration Risk [Member] | Major Customer 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers			$ 35,800
Concentration risk, percentage			19.00%
Accounts Receivable | Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage			75.00%		82.00%
Accounts receivable, major customers	41,900		$ 41,900		$ 32,100
Oil and Gas, Exploration and Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	101,716	32,351	172,974	$ 62,424
Oil and Condensate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,533	2,043	8,479	4,345
Natural Gas, Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,912	1,880	6,702	4,223
Oil and Gas, Refining and Marketing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	153		245
Natural Gas, Gathering, Transportation, Marketing and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost of Goods and Services Sold	4,574	$ 2,555	7,933	$ 5,106
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic	(2,521)		7,774
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Oil and Gas, Exploration and Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	101,716		172,974
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Oil and Condensate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6,103		9,495
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Natural Gas, Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,912		6,702
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Oil and Gas, Refining and Marketing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	153		245
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Natural Gas, Gathering, Transportation, Marketing and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost of Goods and Services Sold	5,144		8,949
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic, Increase (Decrease)	0		0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Oil and Gas, Exploration and Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax, Increase (Decrease)	0		0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Oil and Condensate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax, Increase (Decrease)	(570)		(1,016)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Natural Gas, Production [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax, Increase (Decrease)	0		0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Oil and Gas, Refining and Marketing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue from Contract with Customer, Including Assessed Tax, Increase (Decrease)	0		0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Natural Gas, Gathering, Transportation, Marketing and Processing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Cost of Goods and Services Sold, Increase (Decrease)	$ (570)		$ (1,016)