Pension and Postretirement Benefit Costs (Tables)

3 Months Ended

Mar. 31, 2017

Pension Plan [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

Net periodic pension cost included the following components:

	Three Months Ended
	March 31,
	2017			2016
	(Dollars in millions)
Service cost for benefits earned	$	0.6		$	0.6
Interest cost on projected benefit obligation	9.7			10.4
Expected return on plan assets	(11.0		)	(11.3		)
Amortization of prior service cost and net actuarial loss	6.4			6.2
Net periodic pension cost	$	5.7		$	5.9

Other Postretirement Benefits Plan [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

Net periodic postretirement benefit cost included the following components:

	Three Months Ended
	March 31,
	2017		2016
	(Dollars in millions)
Service cost for benefits earned	$	2.3	$	2.6
Interest cost on accumulated postretirement benefit obligation	8.4		8.8
Amortization of prior service cost and net actuarial loss	3.2		2.4
Net periodic postretirement benefit cost	$	13.9	$	13.8