Pension and Postretirement Benefit Costs (Tables)

9 Months Ended

Sep. 30, 2017

Defined benefit pension plans

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

Schedule of Net Benefit Costs

Net periodic pension (income) cost included the following components:

	Successor			Predecessor			Successor			Predecessor
	Three Months Ended September 30, 2017			Three Months Ended September 30, 2016			April 2 through September 30, 2017			January 1 through April 1, 2017			Nine Months Ended September 30, 2016
	(Dollars in millions)
Service cost for benefits earned	$	0.5		$	0.7		$	1.1		$	0.6		$	2.0
Interest cost on projected benefit obligation	9.4			10.3			18.7			9.7			31.0
Expected return on plan assets	(11.2		)	(11.3		)	(22.4		)	(11.0		)	(33.9		)
Amortization of prior service cost and net actuarial loss	—			6.3			—			6.4			18.8
Net periodic pension (income) cost	$	(1.3	)	$	6.0		$	(2.6	)	$	5.7		$	17.9

Postretirement benefit plans

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

Schedule of Net Benefit Costs

Net periodic postretirement benefit cost included the following components:

	Successor		Predecessor		Successor		Predecessor
	Three Months Ended September 30, 2017		Three Months Ended September 30, 2016		April 2 through September 30, 2017		January 1 through April 1, 2017		Nine Months Ended September 30, 2016
	(Dollars in millions)
Service cost for benefits earned	$	2.3	$	2.6	$	4.6	$	2.3	$	7.8
Interest cost on accumulated postretirement benefit obligation	8.2		8.8		16.5		8.4		26.4
Amortization of prior service cost and net actuarial loss	—		2.4		—		3.2		7.1
Net periodic postretirement benefit cost	$	10.5	$	13.8	$	21.1	$	13.9	$	41.3