Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2016

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following table sets forth, by level within the fair value hierarchy, the Company’s financial assets and liabilities (as applicable) that were accounted for at fair value on a recurring basis as of September 30, 2016 and 2015. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The fair value presentation for over-the-counter swaps combines gas and oil swaps because a significant number of the counterparties enter into both gas and oil swap agreements with the Company.

	At Fair Value as of September 30, 2016
Recurring Fair Value Measures	Level 1		Level 2		Level 3		Netting Adjustments(1)			Total(1)
	(Dollars in thousands)
Assets:
Cash Equivalents — Money Market Mutual Funds	$	113,407	$	—	$	—	$	—		$	113,407
Derivative Financial Instruments:
Commodity Futures Contracts — Gas	2,623		—		—		(2,276		)	347
Over the Counter Swaps — Gas and Oil	—		119,654		—		(3,860		)	115,794
Foreign Currency Contracts	—		—		—		(2,337		)	(2,337		)
Other Investments:
Balanced Equity Mutual Fund	36,658		—		—		—			36,658
Fixed Income Mutual Fund	31,395		—		—		—			31,395
Common Stock — Financial Services Industry	2,902		—		—		—			2,902
Hedging Collateral Deposits	1,484		—		—		—			1,484
Total	$	188,469	$	119,654	$	—	$	(8,473	)	$	299,650
Liabilities:
Derivative Financial Instruments:
Commodity Futures Contracts — Gas	$	2,276	$	—	$	—	$	(2,276	)	$	—
Over the Counter Swaps — Gas and Oil	—		5,322		—		(3,860		)	1,462
Foreign Currency Contracts	—		2,337		—		(2,337		)	—
Total	$	2,276	$	7,659	$	—	$	(8,473	)	$	1,462
Total Net Assets/(Liabilities)	$	186,193	$	111,995	$	—	$	—		$	298,188

	At Fair Value as of September 30, 2015
Recurring Fair Value Measures	Level 1		Level 2		Level 3		Netting Adjustments(1)			Total(1)
	(Dollars in thousands)
Assets:
Cash Equivalents — Money Market Mutual Funds	$	92,196	$	—	$	—	$	—		$	92,196
Derivative Financial Instruments:
Commodity Futures Contracts — Gas	6,373		—		—		(6,373		)	—
Over the Counter Swaps — Gas and Oil	—		272,335		1,791		(808		)	273,318
Foreign Currency Contracts	—		—		—		(2,955		)	(2,955		)
Other Investments:
Balanced Equity Mutual Fund	34,884		—		—		—			34,884
Fixed Income Mutual Fund	8,004		—		—		—			8,004
Common Stock — Financial Services Industry	4,318		—		—		—			4,318
Other Common Stock	450		—		—		—			450
Hedging Collateral Deposits	11,124		—		—		—			11,124
Total	$	157,349	$	272,335	$	1,791	$	(10,136	)	$	421,339
Liabilities:
Derivative Financial Instruments:
Commodity Futures Contracts — Gas	$	15,276	$	—	$	—	$	(6,373	)	$	8,903
Over the Counter Swaps — Gas and Oil	—		1,981		—		(808		)	1,173
Foreign Currency Contracts	—		2,955		—		(2,955		)	—
Total	$	15,276	$	4,936	$	—	$	(10,136	)	$	10,076
Total Net Assets/(Liabilities)	$	142,073	$	267,399	$	1,791	$	—		$	411,263

(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.

Fair Value Measurements Using Unobservable Inputs (Level 3)

All settlements of the derivative financial instruments are reflected in the Gains/Losses Realized and Included in Earnings column of the tables below (amounts in parentheses indicate credits in the derivative asset/liability accounts).

Fair Value Measurements Using Unobservable Inputs (Level 3)

			Total Gains/Losses
	October 1, 2015		(Gains)/Losses Realized and Included in Earnings				Gains/(Losses) Unrealized and Included in Other Comprehensive  Income (Loss)		Transfer In/(Out) of Level 3		September 30, 2016
	(Dollars in thousands)
Derivative Financial Instruments(2)	$	1,791	$	(2,002	)	(1)	$	211	$	—	$	—

(1) Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the year ended September 30, 2016.

(2) Derivative Financial Instruments are shown on a net basis.

			Total Gains/Losses
	October 1, 2014		(Gains)/Losses Realized and Included in Earnings				Gains/(Losses) Unrealized and Included in Other Comprehensive  Income (Loss)		Transfer In/(Out) of Level 3		September 30, 2015
	(Dollars in thousands)
Derivative Financial Instruments(2)	$	1,368	$	(12,738	)	(1)	$	13,161	$	—	$	1,791

(1) Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the year ended September 30, 2015.

(2) Derivative Financial Instruments are shown on a net basis.