Pension and Postretirement Benefit Costs (Tables)

6 Months Ended

Jun. 30, 2016

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						Six Months Ended
	June 30,						June 30,
	2016			2015			2016			2015
	(Dollars in millions)
Service cost for benefits earned	$	0.7		$	0.7		$	1.3		$	1.3
Interest cost on projected benefit obligation	10.3			10.1			20.7			20.2
Expected return on plan assets	(11.3		)	(12.1		)	(22.6		)	(24.1		)
Amortization of prior service cost and net actuarial loss	6.3			10.2			12.5			20.4
Net periodic pension cost	$	6.0		$	8.9		$	11.9		$	17.8

Other Postretirement Benefit 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				Six Months Ended
	June 30,				June 30,
	2016		2015		2016		2015
	(Dollars in millions)
Service cost for benefits earned	$	2.6	$	2.8	$	5.2	$	5.6
Interest cost on accumulated postretirement benefit obligation	8.6		8.4		17.1		16.9
Amortization of prior service cost and net actuarial loss	2.3		4.5		4.7		9.0
Net periodic postretirement benefit cost	$	13.5	$	15.7	$	27.0	$	31.5