Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Net income	$ 2.6	$ 1.2
Derivative activity:
Reclassification of earnings, net of income tax	(0.2)	(0.2)
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.0	0.0
Other comprehensive loss	(0.2)	(0.2)
NET COMPREHENSIVE INCOME	2.4	1.0
Subsidiaries [Member]
Net income	9.4	9.6
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.4	0.1
Other comprehensive loss	0.4	0.1
NET COMPREHENSIVE INCOME	9.8	9.7
Retained Earnings [Member] | Subsidiaries [Member]
Net income	9.4
Change in unfunded pension obligation [Member] | Subsidiaries [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income	$ (0.4)	$ (0.1)