Regulation - Narrative (Details) - Texas - Winter Storm Uri incremental costs - Winter Storm Uri - USD ($) $ in Millions	6 Months Ended	12 Months Ended	31 Months Ended
	Mar. 31, 2025	Sep. 30, 2024	Mar. 31, 2025
Regulatory Asset [Line Items]
Regulatory asset, deferred costs			$ 32.4
Regulatory asset, recovered cost	$ 3.6	$ 22.0
Regulatory asset, deferred costs, remaining	6.8		6.8
Other current assets
Regulatory Asset [Line Items]
Regulatory asset, deferred costs, remaining	0.4		0.4
Deferred charges and other assets
Regulatory Asset [Line Items]
Regulatory asset, deferred costs, remaining	$ 6.4		$ 6.4