Supplementary Financial Information - Schedule of Cash and Cash Equivalents (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Cash, Cash Equivalents, Restricted Cash, And Restricted Cash Equivalents [Roll Forward]
Cash and cash equivalents, beginning of the year	$ 80.8	$ 80.4
Restricted cash included in other current assets, beginning of period	0.9	0.3
Restricted cash included in other assets (non-current), beginning of period	0.6	1.5
Cash, cash equivalents and restricted cash, beginning of year	82.3	82.2
Cash and cash equivalents, end of the year	48.8	80.8
Restricted cash included in other current assets, end of period	0.0	0.9
Restricted cash included in other assets (non-current), end of period	0.5	0.6
Cash, cash equivalents and restricted cash, end of year	49.3	82.3
Total cash, cash equivalents and restricted cash	49.3	82.3
Supplemental cash flow information:
Cash paid for interest	48.6	49.0
Cash paid for income taxes, net of refunds	3.5	6.7
Non-cash investing and financing activities:
Unsecured note issued in connection with purchase of preferred stock and payment of dividends	0.0	35.1
Accrued interest capitalized into principal debt	6.6	1.3
Property, plant and equipment included in accounts payable or accrued expenses	$ 0.5	$ 0.9