PROPERTY AND EQUIPMENT - Summary of property and equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 521,064	$ 444,674
Less: accumulated depreciation and amortization ($11,351 and $6,353 related to capital leases at December 31, 2012 and 2011, respectively)	(272,969)	(246,305)
Property and equipment, net	248,095	198,369
Network equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	129,168	121,477
Network equipment under capital lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,386	5,662
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	17,955	11,387
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	45,011	38,417
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	279,219	231,701
Buildings under capital lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 43,325	$ 36,030

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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Gross amount of long-lived 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, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived 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, furniture and fixtures, and computer equipment.

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