CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Pension Plans [Member]
Pension Plan and Restoration of Retirement Income Plan:
Amortization of prior service cost, net of tax of $0.0, $0.0, $0.1 and $0.0, respectively	$ 0.0	$ 0.0	$ 0.1	$ 0.0
Amortization of deferred net loss, net of tax of $0.0, $0.0, $0.0 and $0.1, respectively	0.0	0.0	0.0	0.1
Regulatory classification of certain pension costs, net of tax of $0.0, $0.0, $0.0 and $1.2, respectively	0.0	0.0	0.0	1.2
Other Postretirement Benefits Plan [Member]
Postretirement plans:
Amortization of deferred net gain, net of tax of $0.0, $0.0, $(0.1) and $0.0, respectively	$ 0.0	$ 0.0	$ (0.1)	$ 0.0