Fair Value Measurements (Narrative) (Details) (USD $)	9 Months Ended
	Jun. 30, 2013		Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Hedging collateral deposits	$ 694,000	[1]	$ 364,000	[1]
Assumed 12 month basis differential comparison to NYMEX	109.30%
Assumed 12 month minimum basis differential comparison to NYMEX	102.30%
Assumed 12 month maximum basis differential comparison to NYMEX	112.40%
Fair Value Measured On Recurring Basis, Net	221,695,000	[1]	79,363,000	[1]
Over The Counter Swaps - Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measured On Recurring Basis, Net	(7,900,000)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Hedging collateral deposits	694,000		364,000
Fair Value Measured On Recurring Basis, Net	159,915,000		77,862,000
Fair Value, Inputs, Level 1 [Member] | NYMEX Futures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Hedging collateral deposits	700,000		400,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Hedging collateral deposits	0		0
Fair Value Measured On Recurring Basis, Net	(7,927,000)		(19,664,000)
Higher [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Basis Differential On NYMEX Sensitivity	10.00%
Fair value of crude oil price swap sensitivity	(9,500,000)
Lower [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Basis Differential On NYMEX Sensitivity	10.00%
Fair value of crude oil price swap sensitivity	$ 1,300,000

[1] Netting Adjustments represent the impact of legally-enforceable master netting arrangements that allow the Company to net gain and loss positions held with the same counterparties. The net asset or net liability for each counterparty is recorded as an asset or liability on the Company’s balance sheet. In the tables above, presenting asset and liability information by gas and oil positions may result in negative assets or negative liabilities in Total column when a counterparty has issued both gas and oil swaps to the Company.