Derivative Instruments - Realized and unrealized gains (losses) on derivative instruments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2024	Mar. 31, 2023	Jun. 30, 2023
Gains and (losses) on derivative instruments
Net unrealized gains on derivative instruments	$ 10,381		$ 13,445
Natural gas swaps
Gains and (losses) on derivative instruments
Gains	41	$ 135
Losses	(8,452)	(9,397)
Total	(8,411)	$ (9,262)
Natural gas swaps \| Regulatory liability
Gains and (losses) on derivative instruments
Net unrealized gains on derivative instruments	$ 10,381		$ 13,445

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Amount of increase in the fair value of derivatives recognized in the income statement.

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Amount of decrease in the fair value of derivatives recognized in the income statement.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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