Regulation - Narrative (Details) - Texas - Winter Storm Uri incremental costs - Winter Storm Uri - USD ($) $ in Millions	9 Months Ended	12 Months Ended	34 Months Ended
	Jun. 30, 2025	Sep. 30, 2024	Jun. 30, 2025
Regulatory Asset [Line Items]
Regulatory asset, deferred costs			$ 32.4
Regulatory asset, recovered cost	$ 4.1	$ 22.0
Regulatory asset, deferred costs, remaining and recorded as a current asset	$ 6.3		$ 6.3