Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Net income	$ 10.2	$ 2.6	$ (5.2)	$ 1.2	$ 12.8	$ (4.0)
Derivative activity:
Reclassification of earnings, net of income tax	(0.3)		(0.2)		(0.5)	(0.4)
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.1		0.1		0.1	0.1
Other comprehensive loss	(0.2)	(0.2)	(0.1)	(0.2)	(0.4)	(0.3)
NET COMPREHENSIVE INCOME / (LOSS)	10.0		(5.3)		12.4	(4.3)
Subsidiaries [Member]
Net income	15.1		(0.4)	9.6	24.5	9.2
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.4		0.1		0.8	0.2
Other comprehensive loss	0.4	0.4	0.1	$ 0.1	0.8	0.2
NET COMPREHENSIVE INCOME / (LOSS)	15.5		$ (0.3)		$ 25.3	$ 9.4
Retained Earnings [Member] | Subsidiaries [Member]
Net income	$ 15.1	$ 9.4