Fair Value Measurements (Recurring Fair Value Measures Of Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	$ 122,024	[1]	$ 46,113	[1]
Hedging Collateral Deposits	694	[1]	364	[1]
Total Assets	223,912	[1]	103,890	[1]
Total Liabilities	2,217	[1]	24,527	[1]
Total Net Assets/(Liabilities)	221,695	[1]	79,363	[1]
Commodity Futures Contracts - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	446	[1]	1,588	[1]
Derivative Financial Instruments	0	[1]	0	[1]
Over The Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	58,162	[1]	26,028	[1]
Derivative Financial Instruments	(2,467)	[1]	4,209	[1]
Over The Counter Swaps - Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	5,835	[1]	0	[1]
Derivative Financial Instruments	4,684	[1]	20,318	[1]
Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	30,125	[1]	24,767	[1]
Common Stock - Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	6,331	[1]	4,758	[1]
Other Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	295	[1]	272	[1]
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	122,024		46,113
Hedging Collateral Deposits	694		364
Total Assets	161,721		80,622
Total Liabilities	1,806		2,760
Total Net Assets/(Liabilities)	159,915		77,862
Fair Value, Inputs, Level 1 [Member] | Commodity Futures Contracts - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	2,252		4,348
Derivative Financial Instruments	1,806		2,760
Fair Value, Inputs, Level 1 [Member] | Over The Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	0		0
Derivative Financial Instruments	0		0
Fair Value, Inputs, Level 1 [Member] | Over The Counter Swaps - Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	0		0
Derivative Financial Instruments	0		0
Fair Value, Inputs, Level 1 [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	30,125		24,767
Fair Value, Inputs, Level 1 [Member] | Common Stock - Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	6,331		4,758
Fair Value, Inputs, Level 1 [Member] | Other Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	295		272
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	0		0
Hedging Collateral Deposits	0		0
Total Assets	72,333		41,751
Total Liabilities	2,626		20,586
Total Net Assets/(Liabilities)	69,707		21,165
Fair Value, Inputs, Level 2 [Member] | Commodity Futures Contracts - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	0		0
Derivative Financial Instruments	0		0
Fair Value, Inputs, Level 2 [Member] | Over The Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	63,255		41,751
Derivative Financial Instruments	2,626		19,932
Fair Value, Inputs, Level 2 [Member] | Over The Counter Swaps - Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	9,078		0
Derivative Financial Instruments	0		654
Fair Value, Inputs, Level 2 [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0		0
Fair Value, Inputs, Level 2 [Member] | Common Stock - Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0		0
Fair Value, Inputs, Level 2 [Member] | Other Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0		0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	0		0
Hedging Collateral Deposits	0		0
Total Assets	17		559
Total Liabilities	7,944		20,223
Total Net Assets/(Liabilities)	(7,927)		(19,664)
Fair Value, Inputs, Level 3 [Member] | Commodity Futures Contracts - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	0		0
Derivative Financial Instruments	0		0
Fair Value, Inputs, Level 3 [Member] | Over The Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	0		0
Derivative Financial Instruments	0		0
Fair Value, Inputs, Level 3 [Member] | Over The Counter Swaps - Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	17		559
Derivative Financial Instruments	7,944		20,223
Fair Value, Inputs, Level 3 [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0		0
Fair Value, Inputs, Level 3 [Member] | Common Stock - Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0		0
Fair Value, Inputs, Level 3 [Member] | Other Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0		0
Netting Adjustments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	0	[1]	0	[1]
Hedging Collateral Deposits	0	[1]	0	[1]
Total Assets	(10,159)	[1]	(19,042)	[1]
Total Liabilities	(10,159)	[1]	(19,042)	[1]
Total Net Assets/(Liabilities)	0	[1]	0	[1]
Netting Adjustments [Member] | Commodity Futures Contracts - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	(1,806)	[1]	(2,760)	[1]
Derivative Financial Instruments	(1,806)	[1]	(2,760)	[1]
Netting Adjustments [Member] | Over The Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	(5,093)	[1]	(15,723)	[1]
Derivative Financial Instruments	(5,093)	[1]	(15,723)	[1]
Netting Adjustments [Member] | Over The Counter Swaps - Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	(3,260)	[1]	(559)	[1]
Derivative Financial Instruments	(3,260)	[1]	(559)	[1]
Netting Adjustments [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0	[1]	0	[1]
Netting Adjustments [Member] | Common Stock - Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	0	[1]	0	[1]
Netting Adjustments [Member] | Other Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	$ 0	[1]	$ 0	[1]

[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.