CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Postretirement plans:
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	$ 0.0	$ 0.0	$ 0.3
Pension Plans [Member]
Pension Plan and Restoration of Retirement Income Plan:
Amortization of prior service cost, net of tax of $0.1, $0.1 and $0.0, respectively	0.1	0.1	0.0
Amortization of deferred net loss, net of tax of $0.2, $0.2 and $0.9, respectively	0.2	0.2	0.9
Net gain (loss) arising during the period, net of tax of $1.0, ($2.4) and $0.0, respectively	1.0	(2.4)	0.0
Prior service cost arising during the period, net of tax of $0.0, $0.0 and ($0.3), respectively	0.0	0.0	(0.3)
Settlement cost, net of tax of $0.4, $4.3 and $2.7, respectively	0.4	4.3	2.7
Other Postretirement Benefits Plan [Member]
Postretirement plans:
Amortization of prior service credit, net of tax of $0.0, ($0.1) and ($0.4), respectively	0.0	(0.1)	(0.4)
Amortization of deferred net (gain) loss, net of tax of ($0.1), $0.0 and $0.0, respectively	(0.1)	0.0	0.0
Net gain (loss) arising during the period, net of tax of ($0.2), $1.7 and ($0.2), respectively	$ (0.2)	$ 1.7	$ (0.2)