Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Summary of the entity's capital lease activity

The tables below summarize our capital lease activity:

	Years Ended December 31,
	2017		2016	2015
	(Dollars in millions)
Assets acquired through capital leases	$	19	10	10
Depreciation expense	9		5	19
Cash payments towards capital leases	8		6	20

	As of December 31,
	2017		2016
	(Dollars in millions)
Assets included in property, plant and equipment	$	57	40
Accumulated depreciation	24		22

Schedule of future annual minimum payments under capital lease

The future annual minimum payments under capital lease arrangements as of December 31, 2017 were as follows:

	Future Minimum Payments
	(Dollars in millions)
Capital lease obligations:
2018	$	14
2019	10
2020	6
2021	2
2022	1
2023 and thereafter	3
Total minimum payments	36
Less: amount representing interest and executory costs	(6		)
Present value of minimum payments	30
Less: current portion	(12		)
Long-term portion	$	18

Schedule of future minimum payments under operating leases

At December 31, 2017, our future rental commitments for operating leases were as follows:

	Future Minimum Payments
	(Dollars in millions)
Operating leases:
2018	$	36
2019	31
2020	24
2021	22
2022	18
2023 and thereafter	46
Total future minimum payments(1)	$	177

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⁽¹⁾  Minimum payments have not been reduced by minimum sublease rentals of $22 million due in the future under non-cancelable subleases.