Employee Benefits - Benefit Obligations and Funded Status of Pension Plans, OPEB and Salaried VEBAs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Salaried VEBA
Change in benefit obligation:
Obligation at beginning of year	$ 78.3	$ 90.2
Service cost	0.1	0.1
Interest cost	1.5	2.5
Prior service cost (credit)	14.0	(12.3)
Actuarial (gain) loss	(6.9)	4.7
Benefits paid	(7.2)	(6.9)
Obligation at end of year	79.8	78.3	$ 90.2
Change in plan assets:
Fair market value of plan assets at beginning of year	60.5	57.6
Actual return on assets	5.9	8.1
Company contributions		1.7
Benefits paid	(7.2)	(6.9)
Fair market value of plan assets at end of year	59.2	60.5	57.6
Net funded status	(20.6)	(17.8)
Cumulative loss recognized in Accumulated Other Comprehensive:
Accumulated net actuarial loss	(1.2)	(11.2)
Prior service cost	(34.6)	(24.1)
Total	(35.8)	(35.3)
Pension Plan
Change in benefit obligation:
Obligation at beginning of year	10.0	8.8
Obligation assumed through acquisition of Warrick	6.5
Foreign currency translation adjustment		0.3
Service cost	4.1	0.3	0.3
Interest cost	0.5	0.3	0.3
Actuarial (gain) loss	(0.3)	0.6
Benefits paid	(0.5)	(0.3)
Obligation at end of year	20.3	10.0	8.8
Change in plan assets:
Fair market value of plan assets at beginning of year	8.7	7.8
Foreign currency translation adjustment		0.2
Actual return on assets	1.1	0.7
Company contributions	0.5	0.3
Benefits paid	(0.5)	(0.3)
Fair market value of plan assets at end of year	9.8	8.7	$ 7.8
Net funded status	(10.5)	(1.3)
Cumulative loss recognized in Accumulated Other Comprehensive:
Accumulated net actuarial loss	(1.0)	(2.1)
Total	(1.0)	$ (2.1)
Other Postretirement Benefits Plan
Change in benefit obligation:
Obligation assumed through acquisition of Warrick	78.1
Service cost	1.1
Interest cost	1.7
Actuarial (gain) loss	2.6
Obligation at end of year	83.5
Change in plan assets:
Net funded status	(83.5)
Cumulative loss recognized in Accumulated Other Comprehensive:
Accumulated net actuarial loss	(2.6)
Total	$ (2.6)