Property and Equipment, Net (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment	$ 55,032,000		$ 55,032,000		$ 44,812,000
Depreciation and amortization expense	2,400,000	6,700,000	1,700,000	5,100,000
Less: accumulated depreciation and amortization	(32,539,000)		(32,539,000)		(26,664,000)
Property and equipment, net	22,493,000		22,493,000		18,148,000
Capital lease	3,800,000		3,800,000		3,800,000
Capital lease, accumulated depreciation	1,700,000		1,700,000		1,200,000
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	25,613,000		25,613,000		18,798,000
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	9,139,000		9,139,000		6,327,000
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	1,758,000		1,758,000		1,545,000
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	16,646,000		16,646,000		16,470,000
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net	4,900,000		4,900,000		5,500,000
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	1,000,000		1,000,000		1,500,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	1,876,000		1,876,000		1,672,000
Other fixed assets not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,700,000		$ 1,700,000		$ 1,700,000