Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

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,
		2019			2018
		(Dollars in millions)
Land	N/A	$	867		871
Fiber, conduit and other outside plant(1)	15-45 years	24,666			23,936
Central office and other network electronics(2)	3-10 years	19,608			18,736
Support assets(3)	3-30 years	7,984			8,020
Construction in progress(4)	N/A	2,300			1,704
Gross property, plant and equipment		55,425			53,267
Accumulated depreciation		(29,346		)	(26,859	)
Net property, plant and equipment		$	26,079		26,408

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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, cable landing stations, data centers, 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.

Schedule of changes to asset retirement obligations

The following table provides asset retirement obligation activity:

	Years Ended December 31,
	2019			2018		2017
	(Dollars in millions)
Balance at beginning of year	$	190		115		95
Accretion expense	11			10		6
Liabilities assumed in acquisition of Level 3(1)	—			58		45
Liabilities settled	(14		)	(14	)	(3	)
Liabilities transferred to Cyxtera	—			—		(20	)
Change in estimate	10			21		(8	)
Balance at end of year	$	197		190		115

(1) The liabilities assumed during 2018 relate to purchase price adjustments during the year.