Property, Plant and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

Property, Plant and Equipment

Property, plant and equipment in service and under construction, and related accumulated depreciation and amortization, as of December 31, 2018 and 2017, were as follows:

December 31,	Useful Lives (Years)	2018			2017
(Dollars in millions)
Land	N/A	$	35		$	36
Buildings	20	296			297
Leasehold and land improvements	1-30	1,210			1,178
Cell site equipment	7-25	3,460			3,411
Switching equipment	5-8	1,018			988
Office furniture and equipment	3-5	285			389
Other operating assets and equipment	3-5	51			57
System development	1-7	1,149			1,060
Work in process	N/A	274			212
Total property, plant and equipment, gross		7,778			7,628
Accumulated depreciation and amortization		(5,576		)	(5,308		)
Total property, plant and equipment, net		$	2,202		$	2,320

Depreciation and amortization expense totaled $627 million, $604 million and $607 million in 2018, 2017 and 2016, respectively. In 2018, 2017 and 2016, (Gain) loss on asset disposals, net included charges of $10 million, $17 million and $22 million, respectively, related to disposals of assets, trade-ins of older assets for replacement assets and other retirements of assets from service in the normal course of business.