Note 9 - Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2023

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

							Effects of
	Quoted						Netting
	Prices		Significant		Significant		and Cash
	in Active		Observable		Unobservable		Margin
	Markets		Inputs		Inputs		Receivables
	(Level 1)		(Level 2)		(Level 3)		/Payables			Total
As of September 30, 2023
ASSETS
Gas Utility:
U.S. stock/bond mutual funds	$	20.4	$	—	$	—	$	—		$	20.4
Gasoline and heating oil contracts		—		0.1		—		(0.1	)		—
NYMEX/ICE natural gas contracts		6.3		—		—		(6.3	)		—
Gas Marketing:
NYMEX/ICE natural gas contracts		10.1		—		—		(10.1	)		—
Natural gas commodity contracts		—		36.7		—		(3.6	)		33.1
Other:
U.S. stock/bond mutual funds		37.6		—		—		—			37.6
Interest rate swaps		—		44.2		—		—			44.2
Total	$	74.4	$	81.0	$	—	$	(20.1	)	$	135.3
LIABILITIES
Gas Utility:
NYMEX/ICE natural gas contracts	$	50.8	$	—	$	—	$	(44.0	)	$	6.8
Gas Marketing:
NYMEX/ICE natural gas contracts		21.8		—		—		(21.8	)		—
Natural gas commodity contracts		—		27.6		—		(3.6	)		24.0
Total	$	72.6	$	27.6	$	—	$	(69.4	)	$	30.8
As of September 30, 2022
ASSETS
Gas Utility:
U.S. stock/bond mutual funds	$	19.1	$	—	$	—	$	—		$	19.1
NYMEX/ICE natural gas contracts		57.8		—		—		(57.8	)		—
Gas Marketing:
NYMEX/ICE natural gas contracts		91.8		—		—		(91.8	)		—
Natural gas commodity contracts *		—		56.6		—		(4.0	)		52.6
Other:
U.S. stock/bond mutual funds		29.3		—		—		—			29.3
Interest rate swaps *		—		63.6		—		—			63.6
Total	$	198.0	$	120.2	$	—	$	(153.6	)	$	164.6
LIABILITIES
Gas Utility:
NYMEX/ICE natural gas contracts	$	30.7	$	—	$	—	$	(30.7	)	$	—
Gas Marketing:
NYMEX/ICE natural gas contracts		82.3		—		—		(82.3	)		—
Natural gas commodity contracts *		—		65.5		—		(4.0	)		61.5
Total	$	113.0	$	65.5	$	—	$	(117.0	)	$	61.5

							Effects of
	Quoted						Netting
	Prices		Significant		Significant		and Cash
	in Active		Observable		Unobservable		Margin
	Markets		Inputs		Inputs		Receivables
	(Level 1)		(Level 2)		(Level 3)		/Payables			Total
As of September 30, 2023
ASSETS
U.S. stock/bond mutual funds	$	20.4	$	—	$	—	$	—		$	20.4
Gasoline and heating oil contracts		—		0.1		—		(0.1	)		—
NYMEX/ICE natural gas contracts		6.3		—		—		(6.3	)		—
Total	$	26.7	$	0.1	$	—	$	(6.4	)	$	20.4
LIABILITIES
NYMEX/ICE natural gas contracts	$	50.8	$	—	$	—	$	(44.0	)	$	6.8
As of September 30, 2022
ASSETS
U.S. stock/bond mutual funds	$	19.1	$	—	$	—	$	—		$	19.1
NYMEX/ICE natural gas contracts		57.8		—		—		(57.8	)		—
Total	$	76.9	$	—	$	—	$	(57.8	)	$	19.1
LIABILITIES
NYMEX/ICE natural gas contracts	$	30.7	$	—	$	—	$	(30.7	)	$	—