CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Other comprehensive income (loss), net of tax
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 73.1	$ 112.9	$ 352.6	$ 165.6
Pension Plan and Restoration of Retirement Income Plan:
Amortization of prior service cost, net of tax of $0.0, $0.0, $0.0 and $0.0, respectively	0.0	0.0	0.1	0.0
Amortization of deferred net loss, net of tax of $0.2, $0.2, $0.3 and $0.4, respectively	0.2	0.2	0.5	0.8
Settlement cost, net of tax of $0.2, $0.6, $2.4 and $1.6, respectively	0.7	0.6	8.1	3.7
Postretirement Benefit Plans:
Amortization of prior service credit, net of tax of $0.0, ($0.1), $0.0 and ($0.2), respectively	0.0	(0.4)	0.0	(0.7)
Amortization of deferred net gain, net of tax of $0.0, $0.0 and $0.0, respectively	0.0	0.1	0.0	0.1
Other comprehensive gain from unconsolidated affiliates, net of tax of $0.0, $0.1, $0.0 and $0.1, respectively	0.0	(0.2)	0.0	(0.3)
Other comprehensive income, net of tax	0.9	0.7	8.7	4.2
Comprehensive income	74.0	113.6	361.3	169.8
Other Comprehensive Income Amortization Of Defined Benefit Pension Plans Net Prior Service Cost Recognized in Net Periodic Pension Cost, Tax	0.0	0.0	0.0	0.0
Amortization of deferred net loss	0.2	0.2	0.3	0.4
Other Comprehensive Income (Loss), Defined Benefit Plan, Adjustment for Settlement or Curtailment Gain (Loss), Tax	0.2	0.6	2.4	1.6
Amortization of prior service cost	0.0	(0.1)	0.0	(0.2)
Other Comprehensive Income Reclassification Of Defined Benefit Postretirement Plans Net Gain Loss Recognized In Net Periodic Benefit Cost Tax	0.0	0.0	0.0	0.0
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	$ 0.0	$ 0.1	$ 0.0	$ 0.1