Long-Term Debt Revolving Credit Facility (Details) - Line of Credit [Member] - Revolving Credit Facility [Member] $ in Thousands		1 Months Ended	3 Months Ended
		May. 04, 2016	Mar. 31, 2016 USD ($)	Apr. 27, 2016 USD ($)	Apr. 08, 2016 USD ($)	Dec. 31, 2015 USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 2,500,000
Borrowing Base, Line of Credit			2,000,000
Line of Credit Facility, Current Borrowing Capacity			1,500,000
Long-term Line of Credit	[1]		293,000			$ 202,000
Letters of Credit Outstanding, Amount	[2]		200			200
Line of Credit Facility, Remaining Borrowing Capacity			$ 1,206,800			$ 1,297,800
Subsequent Event [Member]
Line of Credit Facility [Line Items]
Borrowing Base, Line of Credit					$ 1,250,000
Line of Credit Facility, Current Borrowing Capacity					$ 1,250,000
Percentage of Proved Property Secured for Credit Facility Borrowing					90.00%
Long-term Line of Credit	[1]			$ 294,500
Letters of Credit Outstanding, Amount	[2]			200
Line of Credit Facility, Remaining Borrowing Capacity				$ 955,300
Borrowing Base Utilization Of 25 Percent Or Less [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.30%
Borrowing Base Utilization Of 25 Percent Or Less [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.75%
Borrowing Base Utilization Of 25 Percent Or Less [Member] | Prime Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.75%
Borrowing Base Utilization Of More Than 25 Percent But Less Than 50 Percent [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.30%
Borrowing Base Utilization Of More Than 25 Percent But Less Than 50 Percent [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.00%
Borrowing Base Utilization Of More Than 25 Percent But Less Than 50 Percent [Member] | Prime Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.00%
Borrowing Base Utilization Of More Than 50 Percent But Less Than 75 Percent [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.35%
Borrowing Base Utilization Of More Than 50 Percent But Less Than 75 Percent [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.25%
Borrowing Base Utilization Of More Than 50 Percent But Less Than 75 Percent [Member] | Prime Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%
Borrowing Base Utilization Of More Than 75 Percent But Less Than 90 Percent [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.375%
Borrowing Base Utilization Of More Than 75 Percent But Less Than 90 Percent [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.50%
Borrowing Base Utilization Of More Than 75 Percent But Less Than 90 Percent [Member] | Prime Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Borrowing Base Utilization Of More Than 90 Percent [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.375%
Borrowing Base Utilization Of More Than 90 Percent [Member] | Eurodollar [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.75%
Borrowing Base Utilization Of More Than 90 Percent [Member] | Prime Rate [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.75%
Maximum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Compliance, Debt To Adjusted EBITDAX Ratio			4.0
Maximum [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Compliance, Senior Secured Debt To Adjusted EBITDAX Ratio		2.75
Minimum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Compliance, Adjusted Current Ratio			1.0
Minimum [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Covenant Compliance, Adjusted Current Ratio		1.0
Debt Instrument, Covenant Compliance, Adjusted EBITDAX To Interest Expense		2.0

[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.

[2] Letters of credit outstanding reduce the amount available under the credit facility on a dollar-for-dollar basis.