Employee Benefit Plans

9 Months Ended

Sep. 30, 2022

Retirement Benefits [Abstract]

Employee Benefit Plans

8. Employee Benefit Plans

The components of net periodic cost for our defined benefit pension plan and for our postretirement benefit plan are included in the following tables:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2022			2021			2022			2021
Net Periodic Pension Cost	(Dollars in millions)
Interest cost	$	2.2		$	1.7		$	6.6		$	5.1
Actuarial loss amortization		3.4			4.4			10.2			13.0
Less: Expected return on plan assets		(4.0	)		(3.3	)		(11.9	)		(9.9	)
Net periodic pension cost	$	1.6		$	2.8		$	4.9		$	8.2

	Three Months Ended September 30,						Nine Months Ended September 30,
	2022			2021			2022			2021
Net Periodic Postretirement Benefit	(Dollars in millions)
Interest cost	$	0.1		$	—		$	0.2		$	0.1
Actuarial gain amortization		(0.5	)		(0.5	)		(1.5	)		(1.5	)
Prior service credit amortization		—			(0.1	)		—			(0.2	)
Net periodic postretirement benefit gain	$	(0.4	)	$	(0.6	)	$	(1.3	)	$	(1.6	)