Property and equipment: (Tables)

12 Months Ended

Dec. 31, 2017

Property and equipment:

Schedule of property and equipment

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

	December 31,
	2017			2016
Owned assets:
Network equipment	$	510,327		$	476,786
Leasehold improvements		200,184			182,734
System infrastructure		114,046			102,502
Software		9,701			9,523
Office and other equipment		14,591			13,735
Building		1,334			1,171
Land		113			99
		850,296			786,550
Less—Accumulated depreciation and amortization		(680,114	)		(621,162	)
		170,182			165,388
Assets under capital leases:
IRUs		383,460			349,920
Less—Accumulated depreciation and amortization		(172,360	)		(153,667	)
		211,100			196,253
Property and equipment, net	$	381,282		$	361,641