Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net income	$ 15.4	$ 13.6
Derivative activity:
Reclassification of earnings, net of income tax	(0.1)	(0.2)
Total change in fair value of derivatives	(0.1)	(0.2)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	0.1	0.1
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.2	0.5
Total change in unfunded pension obligation	0.2	0.5
Other comprehensive income	0.1	0.3
Net comprehensive income	15.5	13.9
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	0.1	0.0
Subsidiaries [Member]
Net income	16.9	18.3
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.7	1.0
Total change in unfunded pension obligation	0.7	1.0
Other comprehensive income	0.7	1.0
Net comprehensive income	17.6	19.3
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (0.2)	$ (0.3)