Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash paid during the period for:
Interest (net of amount capitalized)	$ 74.1	$ 73.8
Non-cash investing activities:
Accounts payable and property, plant and equipment	30.5	32.3
Right-of-use asset obtained in exchange for lease obligations	1.0	0.0
Gas stored underground and property, plant and equipment	$ 47.8	$ 0.0