Summary of Significant Accounting Policies Other (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Basis of Presentation and Significant Accounting Policies [Line Items]
Receivables Collection Period		2 months
Allowance for Doubtful Accounts Receivable		$ 1,100	$ 0
Capitalized Computer Software, Gross		$ 44,000	35,000
Concentration of Credit Risk and Major Customers [Abstract]
Marketing agreement length for gathering, transportation, and processing through-put commitments		10 years
Number of Derivative Counterparties		10
Revenues [Abstract]
Revenue Receipt, Days After Sale, Low End of Range		30 days
Revenue Receipt, Days After Sale, High End of Range		90 days
Impairment of Proved, Unproved, and Other Properties [Abstract]
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast		5 years
Impairment of proved properties		$ 468,679	84,480	$ 172,641
Abandonment and impairment of unproved properties		78,643	75,638	46,105
Impairment of other property and equipment		49,369	0	$ 0
Line of Credit [Member]
Basis of Presentation and Significant Accounting Policies [Line Items]
Revolving credit facility	[1]	$ 202,000	$ 166,000
Customer Concentration Risk [Member] | Oil And Gas Sales Revenue [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Number of Major Customers		1	1	3
Customer Concentration Risk [Member] | Oil And Gas Sales Revenue [Member] | Major Customer One [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage		21.00%	19.00%	16.00%
Customer Concentration Risk [Member] | Oil And Gas Sales Revenue [Member] | Major Customer Two [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage				26.00%
Customer Concentration Risk [Member] | Oil And Gas Sales Revenue [Member] | Major Customer Three [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage				12.00%
Customer Concentration Risk [Member] | Oil And Gas Sales Revenue [Member] | Unnamed Major Customer One with Related Entities [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage		10.00%	14.00%
Number of Entities Related to One Unnamed Customer		4
Customer Concentration Risk [Member] | Oil And Gas Sales Revenue [Member] | Unnamed Major Customer Two with Related Entities [Member]
Concentration of Credit Risk and Major Customers [Abstract]
Entity-Wide Revenue, Major Customer, Percentage		11.00%
Number of Entities Related to One Unnamed Customer		3
Oil and Gas Properties [Member]
Property, Plant and Equipment [Abstract]
Property, Plant, and Equipment, Salvage Value		$ 29,700	$ 50,800
Minimum [Member] | Property, Plant and Equipment, Other Types [Member]
Inventory, Net [Abstract]
Property, Plant and Equipment, Estimated Useful Lives		3
Maximum [Member] | Property, Plant and Equipment, Other Types [Member]
Inventory, Net [Abstract]
Property, Plant and Equipment, Estimated Useful Lives		30

[1] Deferred financing costs attributable to the credit facility are presented as a component of other noncurrent assets on the accompanying balance sheets and thus are not deducted from the credit facility balance.