Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The total charge for the use of long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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PROPERTY AND EQUIPMENT - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,067,701				$ 971,685
Less: accumulated depreciation and amortization ($55,198 and $50,253 related to capital leases at December 31, 2018 and 2017, respectively)	(589,640)				(513,120)
Property and equipment, net	478,061	$ 487,616	$ 463,273	$ 471,752	458,565
Accumulated depreciation and amortization related to capital leases	57,641				50,253
Network equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	274,322				247,190
Network equipment under capital lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	14,206				14,206
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	28,583				26,246
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	66,924				43,930
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	414,212				412,631
Buildings under capital lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 269,455				$ 227,482