Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) Purchasers	Dec. 31, 2018 USD ($) $ / bbl	Dec. 31, 2018 USD ($) $ / MMBTU	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) Purchasers	Dec. 31, 2017 USD ($) $ / bbl	Dec. 31, 2017 USD ($) $ / MMBTU	Dec. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) Purchasers	Dec. 31, 2016 USD ($) $ / bbl	Dec. 31, 2016 USD ($) $ / MMBTU	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2019 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stock-based compensation (non-cash) expense						$ 17,200,000					$ 16,654,000					$ 12,362,000
Capitalized general and administrative costs						29,900,000					23,100,000					15,700,000
Restricted cash	$ 19,439,000	$ 19,439,000	$ 19,439,000	$ 19,439,000	$ 19,439,000	19,439,000	$ 5,977,000	$ 5,977,000	$ 5,977,000	$ 5,977,000	5,977,000	$ 1,258,000	$ 1,258,000	$ 1,258,000	$ 1,258,000	1,258,000
Revenue from contract with customer						829,691,000
Billing date	30 days
Outstanding days of account receivable	60 days
Allowance for doubtful accounts	$ 0	$ 0	$ 0	$ 0	$ 0	0
Number of purchasers | Purchasers		4					4					3
Capitalized interest expense						8,800,000					7,300,000					3,700,000
Present value discounted percent of future net revenues of proved oil and natural gas reserves					10.00%
Average oil and natural gas prices			62.04	3.10				47.79	2.98				39.25	2.48
Impairment charge of net capitalized costs						0					0					158,633,000
Common stock and restricted stock unit expense						1,600,000					3,000,000					1,000,000
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer						10,600,000
Cost of revenue						(10,600,000)
Accounting Standards Update 2016-18
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Restricted cash	$ 6,000,000	$ 6,000,000	$ 6,000,000	$ 6,000,000	$ 6,000,000	$ 6,000,000	$ 1,300,000	$ 1,300,000	$ 1,300,000	$ 1,300,000	$ 1,300,000	$ 44,400,000	$ 44,400,000	$ 44,400,000	$ 44,400,000	$ 44,400,000
Minimum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract term after production	1 month
Accounts receivable due period	30 days
Useful life	5 years
Maximum
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Contract term after production	2 months
Accounts receivable due period	60 days
Useful life	30 years
Sales Revenue, Goods, Net
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Concentration risk, percentage					60.00%					60.00%					48.00%
Accounts Receivable
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Concentration risk, percentage					34.00%					43.00%					38.00%
Plains Marketing, L.P. | Customer Concentration Risk | Sales Revenue, Goods, Net
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Concentration risk, percentage					19.00%					14.00%					18.00%
Shell Trading (US) Company | Customer Concentration Risk | Sales Revenue, Goods, Net
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Concentration risk, percentage										12.00%					17.00%
BP America Production Company | Customer Concentration Risk | Sales Revenue, Goods, Net
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Concentration risk, percentage					15.00%
Occidental Energy Marketing, Inc. | Customer Concentration Risk | Sales Revenue, Goods, Net
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Concentration risk, percentage					14.00%					23.00%					13.00%
Western Refining Oil | Customer Concentration Risk | Sales Revenue, Goods, Net
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Concentration risk, percentage					12.00%					11.00%
Machinery and Equipment
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Useful life using the straight-line	30 years
Accumulated Deficit | Subsequent Event | Minimum | Accounting Standards Update 2016-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
RIght-of-use asset																	$ 55,000,000
Lease liability																	55,000,000
Accumulated Deficit | Subsequent Event | Maximum | Accounting Standards Update 2016-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
RIght-of-use asset																	65,000,000
Lease liability																	$ 60,000,000