Employee Benefits - Benefit Obligations and Funded Status of Pension Plans, OPEB and Salaried VEBAs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Salaried VEBA
Change in benefit obligation:
Obligation at beginning of year	$ 79.8	$ 78.3
Service cost	0.1	0.1
Interest cost	1.9	1.5
Prior service cost		14.0
Actuarial (gain) loss	(16.3)	(6.9)
Benefits paid	(6.6)	(7.2)
Obligation at end of year	58.9	79.8	$ 78.3
Change in plan assets:
Fair market value of plan assets at beginning of year	59.2	60.5
Actual return on assets	(10.2)	5.9
Benefits paid	(6.6)	(7.2)
Fair market value of plan assets at end of year	42.4	59.2	60.5
Net funded status	(16.5)	(20.6)
Cumulative gain (loss) recognized in Accumulated Other Comprehensive Income (Loss):
Accumulated net actuarial gain (loss)	1.7	(1.2)
Prior service cost	(29.7)	(34.6)
Total	(28.0)	(35.8)
Pension Plans
Change in benefit obligation:
Obligation at beginning of year	20.3	10.0
Obligation assumed through acquisition of Warrick		6.5
Foreign currency translation adjustment	(0.5)
Service cost	5.8	4.1	0.3
Interest cost	0.6	0.5	0.3
Actuarial (gain) loss	(7.1)	(0.3)
Plan participants contributions	0.1
Benefits paid	(0.4)	(0.5)
Obligation at end of year	18.8	20.3	10.0
Change in plan assets:
Fair market value of plan assets at beginning of year	9.8	8.7
Foreign currency translation adjustment	(0.5)
Actual return on assets	(2.6)	1.1
Plan participants contributions	0.1
Company contributions	8.5	0.5
Benefits paid	(0.4)	(0.5)
Fair market value of plan assets at end of year	14.9	9.8	$ 8.7
Net funded status	(3.9)	(10.5)
Cumulative gain (loss) recognized in Accumulated Other Comprehensive Income (Loss):
Accumulated net actuarial gain (loss)	2.6	(1.0)
Total	2.6	(1.0)
Other Postretirement Benefits Plan
Change in benefit obligation:
Obligation at beginning of year	83.5
Obligation assumed through acquisition of Warrick		78.1
Service cost	1.6	1.1
Interest cost	2.2	1.7
Actuarial (gain) loss	(20.4)	2.6
Plan participants contributions	0.1
Benefits paid	(0.6)
Obligation at end of year	66.4	83.5
Change in plan assets:
Plan participants contributions	0.1
Company contributions	0.5
Benefits paid	(0.6)
Net funded status	(66.4)	(83.5)
Cumulative gain (loss) recognized in Accumulated Other Comprehensive Income (Loss):
Accumulated net actuarial gain (loss)	17.8	(2.6)
Total	$ 17.8	$ (2.6)