Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Schedule of net property, plant and equipment

Net property, plant and equipment is composed of the following:

	Depreciable Lives	As of December 31,
		2018			2017
		(Dollars in millions)
Property, plant and equipment:
Land	N/A	$	332		333
Fiber, conduit and other outside plant(1)	15-45 years	7,171			6,639
Central office and other network electronics(2)	7-10 years	4,361			4,250
Support assets(3)	5-30 years	2,656			2,620
Construction in progress(4)	N/A	508			474
Gross property, plant and equipment		15,028			14,316
Accumulated depreciation		(6,951		)	(6,392	)
Net property, plant and equipment		$	8,077		7,924

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(1) Fiber, conduit and other outside plant consists of fiber and metallic cable, conduit, poles and other supporting structures.

(2) Central office and other network electronics consists of circuit and packet switches, routers, transmission electronics and electronics providing service to customers.

(3) Support assets consist of buildings, computers and other administrative and support equipment.

(4) Construction in progress includes inventory held for construction and property of the aforementioned categories that has not been placed in service as it is still under construction.