Derivative Financial Instruments Derivative Financial Instruments (Schedule of Gas Derivative Contracts Volume and Weighted Average Prices) (Details)		Oct. 28, 2016 MMBTU / d $ / MMBTU	Sep. 30, 2016 MMBTU / d $ / MMBTU
Swap Contracts For Fourth Quarter of Year One [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			70,000
Swap Contracts For Fourth Quarter of Year One [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			4.06
Collar Contracts With Short Puts for Year 2 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			130,000
Collar Contracts With Short Puts for Year 2 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Average Cap Price			3.39
Derivative, Average Floor Price			2.85
Derivative, Notional Amount, Price Per Unit			2.41
Collar Contracts With Short Puts for Year 3 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			50,000
Collar Contracts With Short Puts for Year 3 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Average Cap Price			3.40
Derivative, Average Floor Price			2.75
Derivative, Notional Amount, Price Per Unit			2.25
Swap Contracts for Year 2 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			0
Swap Contracts for Year 2 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.00
Swap Contracts for Year 3 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			0
Swap Contracts for Year 3 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.00
Collar Contracts With Short Puts For Fourth Quarter of Year One [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			180,000
Collar Contracts With Short Puts For Fourth Quarter of Year One [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Average Cap Price			4.01
Derivative, Average Floor Price			3.24
Derivative, Notional Amount, Price Per Unit			2.78
Subsequent Event [Member] | Collar Contracts With Short Puts for Year 2 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d		50,000
Subsequent Event [Member] | Collar Contracts With Short Puts for Year 2 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Average Cap Price		3.76
Derivative, Average Floor Price		3.06
Derivative, Notional Amount, Price Per Unit		2.50
Gulf Coast [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			10,000
Gulf Coast [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.00
Gulf Coast [Member] | Basis Swap Contracts for Year 2 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d	[1]		0
Gulf Coast [Member] | Basis Swap Contracts for Year 2 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.00
Gulf Coast [Member] | Basis Swap Contracts for Year 3 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d	[1]		0
Gulf Coast [Member] | Basis Swap Contracts for Year 3 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.00
Mid-Continent [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			15,000
Mid-Continent [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			(0.32)
Mid-Continent [Member] | Basis Swap Contracts for Year 2 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d	[1]		45,000
Mid-Continent [Member] | Basis Swap Contracts for Year 2 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			(0.32)
Mid-Continent [Member] | Basis Swap Contracts for Year 3 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d	[1],[2]		0
Mid-Continent [Member] | Basis Swap Contracts for Year 3 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.00
Permian Basin [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			34,946
Permian Basin [Member] | Basis Swap Contracts for Fourth Quarter of Year One [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.41
Permian Basin [Member] | So Cal Basis Swap Contracts for Year 2 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			9,863
Permian Basin [Member] | So Cal Basis Swap Contracts for Year 2 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.37
Permian Basin [Member] | So Cal Basis Swap Contracts for Year 3 [Member] | Gas contracts, in MMBTU [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU / d			0
Permian Basin [Member] | So Cal Basis Swap Contracts for Year 3 [Member] | Gas contracts, price per MMBTU [Member]
Derivative [Line Items]
Derivative, Swap Type, Average Fixed Price			0.00

[1] (a)During the period from October 1, 2016 through October 28, 2016, the Company entered into additional gas collar contracts with short puts for 50,000 MMBtu per day of 2017 production with a ceiling price of $3.76 per MMBtu, a floor price of $3.06 per MMBtu and a short put price of $2.50 per MMBtu.

[2] Represent swaps that fix the basis differentials between the index prices at which the Company sells its Gulf Coast and Mid-Continent gas, respectively, and the HH index price used in gas swap and collar contracts with short puts.