Pension and Postretirement Benefit Costs (Tables)

3 Months Ended

Mar. 31, 2022

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

Net periodic pension credit included the following components:

	Three Months Ended March 31,
	2022		2021
	(Dollars in millions)
Interest cost on projected benefit obligation	$	5.3	$	5.1
Expected return on plan assets	(5.9)		(5.7)
Net periodic pension credit	$	(0.6)	$	(0.6)

Net periodic postretirement benefit credit included the following components:

	Three Months Ended March 31,
	2022		2021
	(Dollars in millions)
Service cost for benefits earned	$	0.2	$	0.2
Interest cost on accumulated postretirement benefit obligation	1.7		2.9
Expected return on plan assets	(0.2)		(0.2)
Amortization of prior service credit	(13.4)		(11.0)
Net periodic postretirement benefit credit	$	(11.7)	$	(8.1)