Property, Plant and Equipment

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

Property, Plant and Equipment

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

	Depreciable Lives	As of December 31,
		2019			2018
		(Dollars in millions)
Property, plant and equipment:
Land	N/A	$	332		332
Fiber, conduit and other outside plant(1)	15-45 years	7,735			7,171
Central office and other network electronics(2)	7-10 years	4,641			4,361
Support assets(3)	5-30 years	2,670			2,656
Construction in progress(4)	N/A	538			508
Gross property, plant and equipment		15,916			15,028
Accumulated depreciation		(7,746		)	(6,951	)
Net property, plant and equipment		$	8,170		8,077

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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.

We recorded depreciation expense of $831 million, $855 million and $912 million for the years ended December 31, 2019, 2018 and 2017, respectively.