Fair Value Measurements (Recurring Fair Value Measures Of Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	$ 87,836		$ 46,113
Hedging Collateral Deposits	750		364
Total Assets	131,270		103,890
Total Liabilities	41,498		24,527
Total Net Assets/(Liabilities)	89,772		79,363
Commodity Futures Contracts - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	1,547		1,588
Derivative Financial Instruments	0		0
Over The Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Financial Instruments	4,924		26,028
Derivative Financial Instruments	22,300		4,209
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	19,198		20,318
Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	30,084		24,767
Common Stock - Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	5,817		4,758
Other Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Investments	312		272
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	87,836		46,113
Hedging Collateral Deposits	750		364
Total Assets	128,500		80,622
Total Liabilities	2,154		2,760
Total Net Assets/(Liabilities)	126,346		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	3,701		4,348
Derivative Financial Instruments	2,154		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	30,084		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	5,817		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	312		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	24,912		41,751
Total Liabilities	44,880		20,586
Total Net Assets/(Liabilities)	(19,968)		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	24,250		41,751
Derivative Financial Instruments	41,626		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	662		0
Derivative Financial Instruments	3,254		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	0		559
Total Liabilities	16,606		20,223
Total Net Assets/(Liabilities)	(16,606)		(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	0		559
Derivative Financial Instruments	16,606		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	(22,142)	[1]	(19,042)	[1]
Total Liabilities	(22,142)	[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	(2,154)	[1]	(2,760)	[1]
Derivative Financial Instruments	(2,154)	[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	(19,326)	[1]	(15,723)	[1]
Derivative Financial Instruments	(19,326)	[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	(662)	[1]	(559)	[1]
Derivative Financial Instruments	(662)	[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] Amounts represent the impact of legally-enforceable master netting arrangements that allow the Company to net gain and loss positions held with the same counterparties.