CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Parenthetical - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss, net of tax of $1.2, $1.1 and $1.1, respectively	$ 0.9	$ 1.2	$ 1.1
Net loss arising during the period, net of tax of ($1.7), ($2.6) and ($4.7), respectively	0.0	(1.7)	(2.5)
Amortization of prior service credit, net of tax of $0.0, $0.0 and $0.0, respectively	0.0	0.0	0.0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Tax	(0.3)	0.0	(0.1)
Postretirement plans:
Amortization of deferred net gain, net of tax of $0.0, $0.0 and $0.0, respectively	0.0	0.0	0.0
Net gain (loss) arising during the period, net of tax of ($0.8), ($0.1) and $0.7, respectively	(0.2)	(0.8)	(0.1)
Amortization of prior service credit, net of tax of ($0.6), ($0.6) and ($0.6), respectively	(0.4)	(0.6)	(0.6)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	0.3	(0.2)	(0.2)
Pension Plans [Member]
Pension Plan and Restoration of Retirement Income Plan:
Settlement cost, net of tax of $0.7, $2.7 and $1.6, respectively	2.7	0.7	2.7
Other Postretirement Benefits Plan [Member]
Pension Plan and Restoration of Retirement Income Plan:
Settlement cost, net of tax of $0.7, $2.7 and $1.6, respectively	$ 0.0	$ (0.1)	$ 0.0