Operating Revenues - Other Operating Revenues (Details) - Other operating revenues - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Operating Revenues
Other operating revenues	$ 107.7	$ 29.3	$ 80.3
Late payment charges
Disaggregation of Operating Revenues
Other operating revenues	56.5	55.6	54.9
Alternative revenues
Disaggregation of Operating Revenues
Other operating revenues	47.0	(30.3)	21.2
Other
Disaggregation of Operating Revenues
Other operating revenues	$ 4.2	$ 4.0	$ 4.2