Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Net income	$ 0.2	$ 0.4	$ 15.6	$ 14.0
Derivative activity:
Reclassification of earnings, net of income tax	(0.3)	(0.2)	(0.4)	(0.4)
Total change in fair value of derivatives	(0.3)	(0.2)	(0.4)	(0.4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	(0.0)	0.2	0.1	0.3
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.3	0.5	0.5	1.0
Total change in unfunded pension obligation	0.3	0.5	0.5	1.0
Other comprehensive income	0.0	0.3	0.1	0.6
Net comprehensive income	0.2	0.7	15.7	14.6
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	0.0	0.1	0.1	0.1
Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income	0.0	0.3	0.1	0.6
Subsidiaries [Member]
Net income	7.3	8.6	24.2	26.9
Pension and postretirement activity:
Reclassification to earnings, net of income tax	0.7	0.9	1.4	1.9
Total change in unfunded pension obligation	0.7	0.9	1.4	1.9
Other comprehensive income	0.7	0.9	1.4	1.9
Net comprehensive income	8.0	9.5	25.6	28.8
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	(0.2)	(0.3)	(0.4)	(0.6)
Subsidiaries [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income	0.7	0.9	1.4	1.9
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income		(0.2)		(0.4)
Change in unfunded pension obligation [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income		0.5		1.0
Change in unfunded pension obligation [Member] | Subsidiaries [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Net income	$ 0.7	$ 0.9	$ 1.4	$ 1.9