PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Property and equipment consisted of the following (in thousands):



	December 31,
	2019			2018
Network equipment	$	309,323		$	274,680
Network equipment under capital lease	—			14,206
Furniture and equipment	27,681			28,583
Software	50,048			66,924
Leasehold improvements	372,492			414,212
Buildings under capital lease	—			271,226
Property and equipment, gross	759,544			1,069,831
Less: accumulated depreciation and amortization ($55,198 related to capital leases at December 31, 2018)	(544,433		)	(585,525		)
	$	215,111		$	484,306

During the year ended December 31, 2019, we disposed or retired $14.9 million of property and equipment, excluding leasehold improvements, with accumulated depreciation of $13.7 million. During the year ended December 31, 2018 and 2017, we disposed or retired $4.4 million and $9.2 million, respectively, of property and equipment, excluding leasehold improvements, with accumulated depreciation of $4.2 million and $7.3 million, respectively.

During the year ended December 31, 2019, we determined that we would not use certain leasehold improvements from a recently exited data center property in the United States and recorded an impairment of $4.5 million. At the time of disposal, the leasehold improvements had a cost of $37.1 million with accumulated depreciation of $32.6 million. During the year ended December 31 2018, there were no impairments in leasehold improvements. During the year ended December 31, 2017, we determined that we would not use certain leasehold improvements from an exited data center property and recorded an impairment of $0.5 million. At the time of disposal, the leasehold improvements had a cost of $22.4 million with accumulated depreciation of $21.9 million.

Depreciation and amortization of property and equipment consisted of the following (in thousands):



	Year ended December 31,
	2019		2018		2017
Costs of sales and services	$	76,199	$	73,738	$	68,804
Other depreciation and amortization	5,013		10,644		2,478
Subtotal	81,212		84,382		71,282
Amortization of acquired and developed technologies	4,501		4,034		2,147
Total depreciation and amortization	$	85,713	$	88,416	$	73,429