Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2014

General Discussion of Pension and Other Postretirement Benefits [Abstract]

Schedule of plan obligations and funded status

The following table sets forth the plans' obligations and funded status at December 31:

	Pension Benefits						Other Benefits
	2014			2013			2014			2013
	(Dollars in millions)
Change in benefit obligation:
Benefit obligation, beginning of year	$	40.4		$	43.4		$	24.1		$	26.9
Service cost	1.1			1.2			0.3			0.4
Interest cost	1.8			1.6			1.1			1.0
Change in plan provisions	—			—			—			(0.6		)
Benefits paid	(1.2		)	(1.2		)	(1.1		)	(0.9		)
Actuarial (gain) loss	7.6			(4.6		)	4.4			(2.7		)
Benefit obligation, end of year	$	49.7		$	40.4		$	28.8		$	24.1
Change in fair value of plan assets:
Plan assets, beginning of year	$	—		$	—		$	—		$	—
Employer contribution	1.2			1.2			1.1			0.9
Benefits paid	(1.2		)	(1.2		)	(1.1		)	(0.9		)
Plan assets, end of year	$	—		$	—		$	—		$	—
Underfunded status, end of year	$	(49.7	)	$	(40.4	)	$	(28.8	)	$	(24.1	)

Schedule of amounts recognized in Balance Sheet

Amounts recognized in our consolidated balance sheet as of December 31 consist of:

	Pension Benefits						Other Benefits
	2014			2013			2014			2013
	(Dollars in millions)
Noncurrent assets	$	—		$	—		$	—		$	—
Current liabilities	(1.7		)	(1.7		)	(0.9		)	(1.1		)
Noncurrent liabilities	(48.0		)	(38.7		)	(27.9		)	(23.0		)
Net amount recognized	$	(49.7	)	$	(40.4	)	$	(28.8	)	$	(24.1	)

Schedule of amounts recognized in accumulated other comprehensive income

Amounts recognized in accumulated other comprehensive income as of December 31 consist of:

	Pension Benefits				Other Benefits
	2014		2013		2014		2013
	(Dollars in millions)
Prior service cost	$	—	$	—	$	0.1	$	0.3
Net loss (gain)	5.3		0.7		6.1		3.6
	$	5.3	$	0.7	$	6.2	$	3.9

Schedule of accumulated benefit obligations in excess of fair value of plan assets

The following table sets forth our plans with an accumulated benefit obligation in excess of plan assets at December 31:

	Pension Benefits				Other Benefits
	2014		2013		2014		2013
	(Dollars in millions)
Projected benefit obligation	$	49.7	$	40.4	$	28.8	$	24.1
Accumulated benefit obligation	46.1		37.1		28.8		24.1
Fair value of plan assets	—		—		—		—

Schedule of net benefit costs

Components of net periodic benefit cost recognized in our consolidated statements of operations as general and administrative expense for years ended December 31:

	Pension Benefits						Other Benefits
	2014		2013		2012		2014		2013		2012
	(Dollars in millions)
Service cost	$	1.1	$	1.2	$	1.7	$	0.3	$	0.4	$	0.4
Interest cost	1.8		1.6		1.8		1.1		1.0		1.1
Amortization of prior service cost	—		—		—		0.4		0.1		0.1
Amortization of net loss (gain)	—		0.5		1.2		0.2		1.9		2.9
Net periodic benefit cost	$	2.9	$	3.3	$	4.7	$	2.0	$	3.4	$	4.5

Schedule of assumptions used

Additional Information

	Pension Benefits				Other Benefits
	2014		2013		2014		2013
Assumptions
Weighted average assumptions used to determine benefit obligations at December 31:
Discount rate	3.7	%	4.5	%	3.9	%	4.8	%
Rate of compensation increase	6.0	%	6.0	%	3.5	%	3.5	%

	Pension Benefits						Other Benefits
	2014		2013		2012		2014		2013		2012
Weighted average assumptions used to determine net cost for years ended December 31:
Discount rate	4.5	%	3.7	%	4.4	%	4.8	%	4.0	%	4.5	%
Rate of compensation increase	6.0	%	6.0	%	5.9	%	3.5	%	3.5	%	3.5	%

Schedule of assumed health care cost trend rates

	2014					2013
Assumed Health Care Cost Trend Rates at December 31:
Health care cost trend rates assumed for next year	6.5	%	to	12.8	%	7.3	%	to	16.3	%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	5%					5%
Years that the rate reaches the ultimate trend rate	2024		to	2024		2022		to	2023

Schedule of effect of a one-percent-point change in assumed health care cost trend rates

Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects for the year ended December 31, 2014:

	1-Percentage Point Increase		1-Percentage Point Decrease
	(Dollars in millions)
Effect on total of service and interest cost	$	0.2	$	(0.2	)
Effect on postretirement benefit obligation	$	4.7	$	(3.8	)

Schedule of estimated future benefit payments

We estimate that benefit payments related to our pension and postretirement health and life plans over the next ten years will be as follows:

	Pension Benefits		Other Benefits
	(Dollars in millions)
2015	$	1.7	$	0.9
2016	2.9		1.0
2017	2.9		1.0
2018	2.8		1.1
2019	2.8		1.1
Years 2019—2024	16.7		6.7