Revenue - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Commercial And Industrial
Disaggregation Of Revenue [Line Items]
Total operating revenues		$ 150.0		$ 150.0
Off System And Other Incentive
Disaggregation Of Revenue [Line Items]
Total operating revenues	$ 25.0
Other Customer Revenue
Disaggregation Of Revenue [Line Items]
Total operating revenues			$ 25.0		$ 25.0