Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash paid during the period for:
Amounts included in the measurement of operating lease liabilities	$ 3.3	$ 4.2	$ 4.9
Amounts included in the measurement of finance lease liability	1.1	1.1	1.1
Interest (net of amount capitalized)	150.7	162.1	147.3
Income taxes, net	1.6	0.8	0.7
Non-cash investing activities:
Accounts payable and PPE	63.8	30.4	47.7
Right-of-use asset obtained in exchange for lease obligations	1.0	9.9	3.4
Gas stored underground and PPE	$ 0.0	$ 0.0	$ 47.8