Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended			12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Sep. 30, 2013
Summary Of Significant Accounting Policies [Line Items]
Hedging collateral deposits	$ 0	[1]		$ 1,094,000	[1]
Gas stored underground - current	(36,047,000)			(51,484,000)
Capitalized costs of unproved properties excluded from amortization	130,300,000			106,100,000
Full cost ceiling test discount factor	10.00%
Amount full cost ceiling exceeds book value of oil and gas properties	166,900,000
Antidilutive securities	272		422,681
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Gas stored underground - current	7,003,000			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	0
Non-performance Based Restricted Stock Units [Member]
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period	80,951
Granted in fiscal year, weighted average grant date fair value	$ 65.23
Performance Shares [Member]
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period	116,090
Granted in fiscal year, weighted average grant date fair value	$ 67.16
Exchange-Traded Futures Contracts [Member]
Summary Of Significant Accounting Policies [Line Items]
Hedging collateral deposits	$ 0			$ 1,100,000

[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.