Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property and equipment
Property and equipment, gross	$ 166,794	$ 128,932
Less accumulated depreciation and amortization	(100,625)	(74,773)
Property and equipment, net	66,169	54,159
Network equipment
Property and equipment
Property and equipment, gross	53,959	44,262
Internally developed software costs
Property and equipment
Property and equipment, gross	49,854	37,104
Property and equipment, net	16,100	12,200
Machinery and equipment
Property and equipment
Property and equipment, gross	18,431	17,755
Computer equipment
Property and equipment
Property and equipment, gross	15,458	11,656
Leasehold improvements
Property and equipment
Property and equipment, gross	14,452	5,666
Purchased software
Property and equipment
Property and equipment, gross	9,742	9,290
Furniture and fixtures
Property and equipment
Property and equipment, gross	$ 4,898	$ 3,199

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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