4. Property and equipment

The following is a summary of property and equipment, at cost less accumulated depreciation and amortization:

	September 30, 2017			December 31, 2016
Leasehold improvements	$	405,712		$	358,477
Software	39,481			33,349
Construction in progress	22,249			18,859
Computer equipment	12,437			10,878
Furniture, fixtures and office equipment	1,792			1,760

Total property and equipment	481,671			423,323
Less: accumulated depreciation and amortization	(220,661		)	(172,558		)

Total property and equipment, net	$	261,010		$	250,765

Depreciation and amortization expense, which includes depreciation and amortization for property and equipment under capital leases, is allocated as follows in the accompanying condensed consolidated statements of operations:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016

Network access	$	11,625	$	7,227	$	29,354	$	18,689
Network operations	3,987		3,733		12,273		10,183
Development and technology	2,375		1,881		6,840		5,172
General and administrative	258		252		777		757

Total depreciation and amortization of property and equipment	$	18,245	$	13,093	$	49,244	$	34,801

During the nine months ended September 30, 2017, we recognized $166 of impairment losses primarily related to construction in progress projects that were abandoned. During the nine months ended September 30, 2017, we also recognized $276 of losses on disposals of property and equipment.