Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2025

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, 2025 and 2024. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.

	At Fair Value as of September 30, 2025
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	$	30,551	$	—	$	—	$	—	$	30,551
Derivative Financial Instruments:
Over the Counter Swaps — Gas	—		62,190		—		(33,615)		28,575
Over the Counter No Cost Collars — Gas	—		24,149		—		(12,805)		11,344
Foreign Currency Contracts	—		144		—		(675)		(531)
Other Investments:
Balanced Equity Mutual Fund	13,786		—		—		—		13,786
Fixed Income Mutual Fund	10,082		—		—		—		10,082
Total	$	54,419	$	86,483	$	—	$	(47,095)	$	93,807
Liabilities:
Derivative Financial Instruments:
Over the Counter Swaps — Gas	$	—	$	34,169	$	—	$	(33,615)	$	554
Over the Counter No Cost Collars — Gas	—		18,036		—		(12,805)		5,231
Foreign Currency Contracts	—		893		—		(675)		218
Total	$	—	$	53,098	$	—	$	(47,095)	$	6,003
Total Net Assets/(Liabilities)	$	54,419	$	33,385	$	—	$	—	$	87,804

	At Fair Value as of September 30, 2024
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	$	29,238	$	—	$	—	$	—	$	29,238
Derivative Financial Instruments:
Over the Counter Swaps — Gas	—		76,009		—		(17,198)		58,811
Over the Counter No Cost Collars — Gas	—		32,584		—		(3,774)		28,810
Contingent Consideration for Asset Sale	—		729		—		—		729
Foreign Currency Contracts	—		281		—		(726)		(445)
Other Investments:
Balanced Equity Mutual Fund	19,523		—		—		—		19,523
Fixed Income Mutual Fund	17,374		—		—		—		17,374
Total	$	66,135	$	109,603	$	—	$	(21,698)	$	154,040
Liabilities:
Derivative Financial Instruments:
Over the Counter Swaps — Gas	$	—	$	22,206	$	—	$	(17,198)	$	5,008
Over the Counter No Cost Collars — Gas	—		3,501		—		(3,774)		(273)
Foreign Currency Contracts	—		726		—		(726)		—
Total	$	—	$	26,433	$	—	$	(21,698)	$	4,735
Total Net Assets/(Liabilities)	$	66,135	$	83,170	$	—	$	—	$	149,305

(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.

Schedule of Fair Value Measurements, Nonrecurring

The following table presents impairments of assets associated with certain nonrecurring fair value measurements within Level 3 of the fair value hierarchy as of September 30, 2025, 2024 and 2023 (in thousands):

					Impairments
Nonrecurring Fair Value Measures					Year Ended September 30,
	Segment	Date of Measurement	Fair Value		2025		2024		2023
Impairment of Assets:
Water Disposal Assets	Integrated Upstream and Gathering	December 31, 2024	$	12,880	$	33,453	$	—	$	—
Northern Access Project	Pipeline and Storage	September 30, 2024	$	12,133	—		46,075		—
Water Disposal Assets	Integrated Upstream and Gathering	September 30, 2024	$	3,000	—		9,362		—
Total Impairment					$	33,453	$	55,437	$	—