Pension and Savings Plans (Tables) - Pension Plans, Defined Benefit [Member]

12 Months Ended

Dec. 31, 2016

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

Net periodic pension cost included the following components:



	Year Ended December 31,
	2016			2015			2014
	(Dollars in millions)
Service cost for benefits earned	$	2.5		$	2.7		$	2.1
Interest cost on projected benefit obligation	41.5			40.4			45.4
Expected return on plan assets	(45.3		)	(48.2		)	(54.3		)
Amortization of prior service cost	0.3			1.0			1.3
Amortization of net actuarial losses	24.7			39.6			30.2
Settlement charge	—			—			8.7
Net periodic pension cost	$	23.7		$	35.5		$	33.4

Amounts recognized in accumulated other comprehensive loss

The following includes pre-tax amounts recorded in "Accumulated other comprehensive loss":



	Year Ended December 31,
	2016			2015			2014
	(Dollars in millions)
Net actuarial loss arising during year	$	6.6		$	30.6		$	79.2
Amortization:
Net actuarial loss	(24.7		)	(39.6		)	(30.2		)
Prior service cost	(0.3		)	(1.0		)	(1.3		)
Settlement charge	—			—			(8.7		)
Total recorded in "Accumulated other comprehensive loss"	$	(18.4	)	$	(10.0	)	$	39.0

Summary of change in benefit obligation, change in plan assets and funded status

The following summarizes the change in benefit obligation, change in plan assets and funded status of the Pension Plans:



	December 31,
	2016			2015
	(Dollars in millions)
Change in benefit obligation:
Projected benefit obligation at beginning of period	$	939.3		$	1,002.5
Service cost	2.5			2.7
Interest cost	41.5			40.4
Benefits paid	(61.1		)	(62.6		)
Actuarial loss (gain)	37.1			(43.7		)
Projected benefit obligation at end of period	959.3			939.3
Change in plan assets:
Fair value of plan assets at beginning of period	757.3			839.8
Actual return (loss) on plan assets	75.7			(26.1		)
Employer contributions	1.1			6.2
Benefits paid	(61.1		)	(62.6		)
Fair value of plan assets at end of period	773.0			757.3
Funded status at end of year	$	(186.3	)	$	(182.0	)
Amounts recognized in the consolidated balance sheets:
Current obligation (included in "Accounts payable and accrued expenses")	$	—		$	(1.6	)
Noncurrent obligation (included in "Other noncurrent liabilities")	(163.5		)	(180.4		)
Liabilities subject to compromise	(22.8		)	—
Net amount recognized	$	(186.3	)	$	(182.0	)

Weighted-average assumptions used to determine benefit obligations

The weighted-average assumptions used to determine the benefit obligations as of the end of each year were as follows:



	December 31,
	2016		2015
Discount rate	4.15	%	4.55	%
Measurement date	December 31, 2016		December 31, 2015

Weighted-average assumptions used to determine net periodic benefit cost

The weighted-average assumptions used to determine net periodic benefit cost during each year were as follows:



	Year Ended December 31,
	2016		2015		2014
Discount rate	4.55	%	4.15	%	4.95	%
Expected long-term return on plan assets	6.00	%	6.25	%	6.85	%
Measurement date	December 31, 2015		December 31, 2014		December 31, 2013

Fair value of assets in the Master Trust by category and by fair value valuation hierarchy

The following tables present the fair value of assets in the Master Trust by asset category and by fair value hierarchy:



	December 31, 2016
	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Mutual funds	$	119.9	$	—	$	—	$	119.9
Corporate bonds	—		265.7		—		265.7
U.S. government securities	25.1		22.7		—		47.8
International government securities	—		12.6		—		12.6
Cash funds	17.8		—		—		17.8
Real estate investment trusts	—		—		14.1		14.1
Total assets at fair value	$	162.8	$	301.0	$	14.1	477.9

Assets measured at net asset value practical expedient ⁽¹⁾
Private mutual funds							186.1
Common collective trusts							109.0
							295.1
Total plan assets							$	773.0



	December 31, 2015
	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Mutual funds	$	107.1	$	—	$	—	$	107.1
Corporate bonds	—		259.4		—		259.4
U.S. government securities	26.8		26.6		—		53.4
International government securities	—		15.0		—		15.0
Cash funds	18.2		—		—		18.2
Real estate investment trusts	—		—		23.0		23.0
Total assets at fair value	$	152.1	$	301.0	$	23.0	476.1

Assets measured at net asset value practical expedient ⁽¹⁾
Private mutual funds							183.9
Common collective trusts							97.3
							281.2
Total plan assets							$	757.3

⁽¹⁾In accordance with Accounting Standards Update 2015-07, investments that are measured at fair value using the net asset value per share practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the total value of assets of the plans.

Summary of changes in the fair value of the Master Trust's Level 3 investments

The table below sets forth a summary of changes in the fair value of the Master Trust’s Level 3 investments:



	Year Ended December 31,
	2016			2015
	(Dollars in millions)
Balance, beginning of year	$	23.0		$	30.2
Realized gains	1.8			3.2
Unrealized gains relating to investments still held at the reporting date	0.2			0.2
Purchases, sales and settlements, net	(10.9		)	(10.6		)
Balance, end of year	$	14.1		$	23.0

Summary of estimated future benefit payments

The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid in connection with the Company's benefit obligation:



	Pension Benefits
	(Dollars in millions)
2017	$	61.7
2018	62.3
2019	62.2
2020	64.0
2021	65.1
Years 2022-2026	312.4