Fair Value Measurements (Tables)

3 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

Schedule of Derivative Assets and Liabilities, Including Receivables and Payables

	Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Effects of Netting and Cash Margin Receivables /Payables			Total
As of December 31, 2024
ASSETS
Gas Utility:
U.S. stock/bond mutual funds	$	24.7	$	—	$	—		$	24.7
NYMEX/ICE natural gas contracts		5.9		—		(5.9	)		—
Gas Marketing:
NYMEX/ICE natural gas contracts		8.8		—		(8.8	)		—
Natural gas commodity contracts		—		44.1		(1.2	)		42.9
Other:
U.S. stock/bond mutual funds		20.8		—		—			20.8
U.S. bonds		15.6		—		—			15.6
Global bonds		6.0		—		—			6.0
Interest rate swaps		—		16.1		—			16.1
Total	$	81.8	$	60.2	$	(15.9	)	$	126.1
LIABILITIES
Gas Utility:
NYMEX/ICE natural gas contracts	$	6.8	$	—	$	(6.8	)	$	—
Gas Marketing:
NYMEX/ICE natural gas contracts		15.1		—		(15.1	)		—
Natural gas commodity contracts		—		29.1		(1.2	)		27.9
Total	$	21.9	$	29.1	$	(23.1	)	$	27.9

	Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Effects of Netting and Cash Margin Receivables /Payables			Total
As of September 30, 2024
ASSETS
Gas Utility:
U.S. stock/bond mutual funds	$	24.3	$	—	$	—		$	24.3
NYMEX/ICE natural gas contracts		3.4		—		(3.4	)		—
Gas Marketing:
NYMEX/ICE natural gas contracts		7.0		—		(7.0	)		—
Natural gas commodity contracts		—		46.0		(3.5	)		42.5
Other:
U.S. stock/bond mutual funds		17.9		—		—			17.9
U.S. bonds		21.9		—		—			21.9
Global bonds		5.9		—		—			5.9
Interest rate swaps		—		0.8		—			0.8
Total	$	80.4	$	46.8	$	(13.9	)	$	113.3
LIABILITIES
Gas Utility:
NYMEX/ICE natural gas contracts	$	13.6	$	—	$	(3.8	)	$	9.8
Gas Marketing:
NYMEX/ICE natural gas contracts		17.7		—		(17.7	)		—
Natural gas commodity contracts		—		24.5		(3.5	)		21.0
Interest rate swaps		—		1.5		—			1.5
Total	$	31.3	$	26.0	$	(25.0	)	$	32.3
As of December 31, 2023
ASSETS
Gas Utility:
U.S. stock/bond mutual funds	$	22.0	$	—	$	—		$	22.0
NYMEX/ICE natural gas contracts		4.7		—		(4.7	)		—
Gas Marketing:
NYMEX/ICE natural gas contracts		13.2		—		(13.2	)		—
Natural gas commodity contracts		—		45.5		(1.4	)		44.1
Other:
U.S. stock/bond mutual funds		14.6		—		—			14.6
U.S. bonds		21.6		—		—			21.6
Global bonds		1.4		—		—			1.4
Interest rate swaps		—		22.7		—			22.7
Total	$	77.5	$	68.2	$	(19.3	)	$	126.4
LIABILITIES
Gas Utility:
NYMEX/ICE natural gas contracts	$	60.7	$	—	$	(60.7	)	$	—
Gasoline and heating oil contracts		—		0.4		(0.4	)		—
Gas Marketing:
NYMEX/ICE natural gas contracts		32.7		—		(32.7	)		—
Natural gas commodity contracts		—		24.5		(1.4	)		23.1
Other:
Interest rate swaps		—		2.0		—			2.0
Total	$	93.4	$	26.9	$	(95.2	)	$	25.1

	Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Effects of Netting and Cash Margin Receivables /Payables			Total
As of December 31, 2024
ASSETS
U.S. stock/bond mutual funds	$	24.7	$	—	$	—		$	24.7
NYMEX/ICE natural gas contracts		5.9		—		(5.9	)		—
Total	$	30.6	$	—	$	(5.9	)	$	24.7
LIABILITIES
NYMEX/ICE natural gas contracts	$	6.8	$	—	$	(6.8	)	$	—
As of September 30, 2024
ASSETS
U.S. stock/bond mutual funds	$	24.3	$	—	$	—		$	24.3
NYMEX/ICE natural gas contracts		3.4		—		(3.4	)		—
Total	$	27.7	$	—	$	(3.4	)	$	24.3
LIABILITIES
NYMEX/ICE natural gas contracts	$	13.6	$	—	$	(3.8	)	$	9.8
As of December 31, 2023
ASSETS
U.S. stock/bond mutual funds	$	22.0	$	—	$	—		$	22.0
NYMEX/ICE natural gas contracts		4.7		—		(4.7	)		—
Total	$	26.7	$	—	$	(4.7	)	$	22.0
LIABILITIES
NYMEX/ICE natural gas contracts	$	60.7	$	—	$	(60.7	)	$	—
Gasoline and heating oil contracts		—		0.4		(0.4	)		—
Total	$	60.7	$	0.4	$	(61.1	)	$	—