STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 47.2	$ (29.6)	$ (18.5)
Other comprehensive income (loss), net of tax-Note 11:
Defined benefit plans	8.2	24.2	(1.6)
Cash flow hedges	1.7	(17.3)	16.6
Other comprehensive income (loss), net of tax	9.9	6.9	15.0
Comprehensive income (loss)	$ 57.1	$ (22.7)	$ (3.5)