Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended			12 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012	Sep. 30, 2012		Sep. 30, 2011
Summary Of Significant Accounting Policies [Line Items]
Revisions to increase operating cash flows and decrease investing cash flows						$ 32,800,000
Revisions to decrease operating cash flows and increase investing cash flows							1,800,000		6,600,000
Hedging collateral deposits	694,000	[1]		694,000	[1]		364,000	[1]
Gas stored underground - current	(22,180,000)			(22,180,000)			(49,795,000)
Capitalized costs of unproved properties excluded from amortization				143,800,000			146,100,000
Full cost ceiling test discount factor	10.00%			10.00%
Amount full cost ceiling exceeds book value of oil and gas properties	199,100,000			199,100,000
Antidilutive securities	180,552		976,870	196,121		833,170
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground - current	22,032,000			22,032,000			0
Stock Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Stock options granted				0
Restricted Shares [Member]
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period				0
Stock Appreciation Right [Member]
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period				412,970
Share based compensation arrangement by share based payment award other than options grants in period weighted average grant date exercise price				$ 53.05
Granted in fiscal year, weighted average grant date fair value				$ 10.66
Non-performance Based Restricted Stock Units [Member]
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period				39,700
Granted in fiscal year, weighted average grant date fair value				$ 50.13
Performance Based Restricted Stock Units [Member]
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period				255,604
Granted in fiscal year, weighted average grant date fair value				$ 49.51
Exchange-Traded Futures Contracts [Member]
Summary Of Significant Accounting Policies [Line Items]
Hedging collateral deposits	$ 700,000			$ 700,000			$ 400,000

[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.