Regulation - Narrative (Details) - Texas - Winter Storm Uri - USD ($) $ in Millions		1 Months Ended	9 Months Ended	12 Months Ended
	Sep. 01, 2022	Mar. 31, 2023	Jun. 30, 2024	Sep. 30, 2023
Extraordinary Gas Cost
Regulatory Asset [Line Items]
Regulatory asset, authorized		$ 3,500.0
Extraordinary Gas Cost | Minimum
Regulatory Asset [Line Items]
Regulatory asset, maturity period		12 years
Extraordinary Gas Cost | Maximum
Regulatory Asset [Line Items]
Regulatory asset, maturity period		18 years
Winter Storm Uri incremental costs
Regulatory Asset [Line Items]
Regulatory asset, deferred costs	$ 32.4
Regulatory asset, deferred costs, remaining			$ 6.4
Winter Storm Uri incremental costs | Other current assets
Regulatory Asset [Line Items]
Regulatory asset, recovering cost			$ 6.1	$ 21.2