STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 8.1	$ 4.5
Other comprehensive income (loss), net of tax
Defined benefit pension plan and Salaried VEBA	0.9	0.7
Cash flow hedges	17.1	8.5
Foreign currency translation		(0.1)
Other comprehensive income, net of tax	18.0	9.1
Comprehensive income	$ 26.1	$ 13.6