Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment	$ 80,136		$ 80,136		$ 71,889
Less: accumulated depreciation and amortization	(50,898)		(50,898)		(45,271)
Property and equipment, net	29,238		29,238		26,618
Depreciation and amortization expense	3,300	$ 2,900	6,400	$ 5,600
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	42,243		42,243		35,576
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	11,812		11,812		10,899
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,843		2,843		2,931
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	20,538		20,538		19,861
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net	7,400		7,400		6,000
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	700		700		1,400
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	2,700		2,700		2,622
Other fixed assets not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,200		$ 2,200		$ 2,800