Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Net income	$ 1.2	$ 15.4
Derivative activity:
Reclassification of earnings, net of income tax	(0.2)	(0.1)
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.0	0.2
Other comprehensive income / (loss)	(0.2)	0.1
Net Comprehensive income	1.0	15.5
Subsidiaries [Member]
Net income	9.6	16.9
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.1	0.7
Other comprehensive income / (loss)	0.1	0.7
Net Comprehensive income	9.7	17.6
Retained Earnings [Member] | Subsidiaries [Member]
Net income	9.6
Change in unfunded pension obligation [Member] | Subsidiaries [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income	$ (0.1)	$ (0.7)