Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

At December 31, 2017, future minimum lease payments required under operating leases having initial or remaining non-cancellable lease terms for the next five years are as follows:

(dollars in millions)
2018	$	7.0
2019	6.0
2020	4.7
2021	2.8
2022	2.6
Thereafter	18.3
Total	$	41.4

Schedule of Change in Asset Retirement Obligation [Table Text Block]

The following table presents the activity for the Company’s asset retirement obligations:

	December 31,
(dollars in millions)	2017		2016
Balance, beginning of period	$	1.8	$	4.8
Liabilities incurred	0.4		—
Liabilities settled	—		(2.0		)
Revision to estimated cash flow	—		(1.1		)
Accretion expense	0.1		0.1
Balance, end of period	$	2.3	$	1.8