Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Net Income	$ 250.9	$ 217.5	$ 220.8
Other Comprehensive (Loss) Income, Before Tax:
Net hedging (loss) gain arising during the period	(15.9)	20.1	56.7
Amounts reclassified into regulatory liabilities	(20.1)	(17.5)	0.0
Amounts reclassified into net income	(11.1)	(2.4)	(1.2)
Net (loss) gain on cash flow hedging derivative instruments	(47.1)	0.2	55.5
Net gain on defined benefit pension and other postretirement plans	0.6	0.2	1.5
Net unrealized gain (loss) on available-for-sale debt securities	0.2	0.1	(0.4)
Other Comprehensive (Loss) Income, Before Tax	(46.3)	0.5	56.6
Income Tax (Benefit) Expense Related to Items of Other Comprehensive Income	(10.8)	0.1	13.0
Other Comprehensive (Loss) Income, Net of Tax	(35.5)	0.4	43.6
Comprehensive Income	$ 215.4	$ 217.9	$ 264.4