Derivative Financial Instruments (Schedule of Gas Derivative Contracts Volume and Weighted Average Prices) (Details)	Nov. 01, 2017 MMBTU / d $ / MMBTU	Sep. 30, 2017 MMBTU / d $ / MMBTU
Swap contracts for Q4 | Gas contracts, in MMBTU
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		0
Price per MMBtu in usd		0.00
Swap contracts for next year | Gas contracts, in MMBTU
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		30,000
Price per MMBtu in usd		3.08
Swap contracts for next year | Gas contracts, in MMBTU | Subsequent event
Derivative [Line Items]
Volume, barrels per day | MMBTU / d	70,000
Price per MMBtu in usd	3.00
Basis Swap Contracts for November 2017 Through March 2018 [Member] | Gas contracts, in MMBTU | Permian Basin | Subsequent event
Derivative [Line Items]
Volume, barrels per day | MMBTU / d	20,000
Basis Swap Contracts for November 2017 Through March 2018 [Member] | Gas contracts, price per MMBTU | Permian Basin | Subsequent event
Derivative [Line Items]
Price differential, dollars per barrel	0.49
Swap contracts for year 3 | Gas contracts, in MMBTU
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		0
Price per MMBtu in usd		0.00
Collar contracts with short puts for Q4 | Gas contracts, in MMBTU
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		300,000
Collar contracts with short puts for Q4 | Gas contracts, price per MMBTU
Derivative [Line Items]
Ceiling, price per barrel		3.60
Floor, price per barrel		2.96
Short put, price per barrel		2.47
Collar contracts with short puts for next year | Gas contracts, in MMBTU
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		62,329
Collar contracts with short puts for next year | Gas contracts, price per MMBTU
Derivative [Line Items]
Ceiling, price per barrel		3.56
Floor, price per barrel		2.91
Short put, price per barrel		2.37
Collar contracts with short puts for year 3 | Gas contracts, in MMBTU
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		0
Collar contracts with short puts for year 3 | Gas contracts, price per MMBTU
Derivative [Line Items]
Ceiling, price per barrel		0.00
Floor, price per barrel		0.00
Short put, price per barrel		0.00
Basis swap contracts for Q4 | Gas contracts, in MMBTU | Mid-Continent
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		45,000
Basis swap contracts for Q4 | Gas contracts, in MMBTU | Permian Basin
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		26,522
Basis swap contracts for Q4 | Gas contracts, price per MMBTU | Mid-Continent
Derivative [Line Items]
Price differential, dollars per barrel		(0.32)
Basis swap contracts for Q4 | Gas contracts, price per MMBTU | Permian Basin
Derivative [Line Items]
Price differential, dollars per barrel		0.30
Basis swap contracts for next year | Gas contracts, in MMBTU | Mid-Continent
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		0
Basis swap contracts for next year | Gas contracts, in MMBTU | Permian Basin
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		51,671
Basis swap contracts for next year | Gas contracts, price per MMBTU | Mid-Continent
Derivative [Line Items]
Price differential, dollars per barrel		0.00
Basis swap contracts for next year | Gas contracts, price per MMBTU | Permian Basin
Derivative [Line Items]
Price differential, dollars per barrel		0.30
Basis swap contracts for year 3 | Gas contracts, in MMBTU | Mid-Continent
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		0
Basis swap contracts for year 3 | Gas contracts, in MMBTU | Permian Basin
Derivative [Line Items]
Volume, barrels per day | MMBTU / d		70,000
Basis swap contracts for year 3 | Gas contracts, in MMBTU | Permian Basin | Subsequent event
Derivative [Line Items]
Volume, barrels per day | MMBTU / d	10,000
Basis swap contracts for year 3 | Gas contracts, price per MMBTU | Mid-Continent
Derivative [Line Items]
Price differential, dollars per barrel		0.00
Basis swap contracts for year 3 | Gas contracts, price per MMBTU | Permian Basin
Derivative [Line Items]
Price differential, dollars per barrel		0.30
Basis swap contracts for year 3 | Gas contracts, price per MMBTU | Permian Basin | Subsequent event
Derivative [Line Items]
Price differential, dollars per barrel	0.32