Summary of Significant Accounting Policies Other (Details)		12 Months Ended
		Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 01, 2017 USD ($)
Basis of Presentation and Significant Accounting Policies [Line Items]
Retained earnings		$ (665,657,000)	$ (794,020,000)
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent		65,890,000	210,455,000
Cash and cash equivalents		313,943,000	9,372,000	$ 18,000
Restricted Cash	[1]	0	3,000,000	0
Cash, cash equivalents, and restricted cash at end of period	[2]	$ 313,943,000	12,372,000	$ 18,000
Accounts Receivable Additional Disclosures [Abstract]
Receivables Collection Period		2 months
Concentration of Credit Risk and Major Customers [Abstract]
Number of individual entities within groups of entities under common ownership that represent more than 10 percent of total production revenue		0
Number of Derivative Counterparties		10
ASU 2016-09 Cumulative Effect Adjustment for Timing of Recognition of Excess Tax Benefits [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Retained earnings					$ (44,300,000)
ASU 2016-09 Cumulative Effect of Actual Forfeiture Rate [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Retained earnings					700,000
Additional Paid in Capital					1,100,000
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent					$ (400,000)
Revolving Credit Facility [Member] | Line of Credit [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Long-term Line of Credit		$ 0
1.50% Senior Convertible Notes Due 2021 [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Senior Notes, face amount		$ 172,500,000	$ 172,500,000
Minimum [Member]
Revenues [Abstract]
Revenue Receipt, Days After Sale		30 days
Maximum [Member]
Revenues [Abstract]
Revenue Receipt, Days After Sale		90 days
Oil and Gas Properties [Member]
Impairment of Proved, Unproved, and Other Properties [Abstract]
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast		5 years
Property, Plant and Equipment, Other Types [Member] | Minimum [Member]
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Estimated Useful Lives		3 years
Property, Plant and Equipment, Other Types [Member] | Maximum [Member]
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Estimated Useful Lives		30 years
Asset Retirement Obligation Costs [Member] | Minimum [Member]
Asset Retirement Obligations [Abstract]
Fair Value Assumptions, Risk Free Interest Rate		5.50%
Asset Retirement Obligation Costs [Member] | Maximum [Member]
Asset Retirement Obligations [Abstract]
Fair Value Assumptions, Risk Free Interest Rate		12.00%
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Major Customer One [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage	[3]	10.00%	5.00%	4.00%
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Major Customer Two [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage	[4]	7.00%	18.00%	21.00%
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Unnamed Major Customer One with Related Entities [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage	[5]	17.00%	15.00%	10.00%
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Unnamed Major Customer Two with Related Entities [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage	[5]	8.00%	8.00%	11.00%

[1] Restricted cash is included in other noncurrent assets on the accompanying balance sheets.

[2] (1) Refer to Note 1 – Summary of Significant Accounting Policies for a reconciliation of cash, cash equivalents, and restricted cash reported to the amounts reported within the accompanying balance sheets.

[3] This major customer is a purchaser of the Company’s production from its Permian region.

[4] This major customer was the operator of the Company’s outside-operated Eagle Ford shale program, which was divested of during the first quarter of 2017. Prior to the divestiture, the Company was party to various marketing agreements, which included certain gathering, transportation, and processing throughput commitments. Because the Company shared with the operator the risk of non-performance by its counterparty purchasers, the Company included the operator as a major customer in the table above. Several of the operator’s counterparty purchasers under these contracts were also direct purchasers of the Company’s production from other areas.

[5] In the aggregate these groups of entities under common ownership represent more than 10 percent of total oil, gas, and NGL production revenue for the period(s) shown, however, none of the individual entities comprising either group represented more than 10 percent of the Company’s total oil, gas, and NGL production revenue.