Fair Value Measurements (Tables)

3 Months Ended

Dec. 31, 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 December 31, 2025 and September 30, 2025. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.  

Recurring Fair Value Measures	At fair value as of December 31, 2025
(Thousands of Dollars)	Level 1		Level 2		Level 3		Netting Adjustments(1)		Total(1)
Assets:
Cash Equivalents – Money Market Mutual Funds	$	260,901	$	—	$	—	$	—	$	260,901
Derivative Financial Instruments:
Over the Counter Swaps – Gas	—		84,228		—		(32,868)		51,360
Over the Counter No Cost Collars – Gas	—		26,413		—		(8,154)		18,259
Foreign Currency Contracts	—		184		—		(439)		(255)
Other Investments:
Balanced Equity Mutual Fund	14,183		—		—		—		14,183
Fixed Income Mutual Fund	10,203		—		—		—		10,203
Total	$	285,287	$	110,825	$	—	$	(41,461)	$	354,651
Liabilities:
Derivative Financial Instruments:
Over the Counter Swaps – Gas	$	—	$	32,868	$	—	$	(32,868)	$	—
Over the Counter No Cost Collars – Gas	—		8,154		—		(8,154)		—
Foreign Currency Contracts	—		594		—		(439)		155
Total	$	—	$	41,616	$	—	$	(41,461)	$	155
Total Net Assets/(Liabilities)	$	285,287	$	69,209	$	—	$	—	$	354,496

Recurring Fair Value Measures	At fair value as of September 30, 2025
(Thousands of Dollars)	Level 1		Level 2		Level 3		Netting Adjustments(1)		Total(1)
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

(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 December 31, 2025 and 2024 (in thousands):

					Impairments
Nonrecurring Fair Value Measures					Quarter Ended December 31,
	Segment	Date of Measurement	Fair Value		2025		2024
Impairment of Assets:
Water Disposal Assets	Integrated Upstream and Gathering	December 31, 2024	$	12,880	$	—	$	33,453