Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment	$ 176,365			$ 160,672
Finance leases - right of use asset	1,591
Less: accumulated depreciation and amortization	(117,660)			(99,230)
Property and equipment, net	58,705			61,442
Depreciation and amortization expense	6,200	$ 6,100	$ 18,900
Capital leases, accumulated depreciation	1,900
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	108,639			93,530
Computer software
Property, Plant and Equipment [Line Items]
Property and equipment	26,114			26,030
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	5,966			5,814
Finance leases - right of use asset
Property, Plant and Equipment [Line Items]
Finance leases - right of use asset	3,503			3,503
Scanner appliances
Property, Plant and Equipment [Line Items]
Property and equipment	15,564			15,356
Scanner appliances and other computer equipment subject to subscription
Property, Plant and Equipment [Line Items]
Property and equipment, net	5,000			7,900
Scanner appliances and other computer equipment not placed in service
Property, Plant and Equipment [Line Items]
Property and equipment	600			1,800
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 16,579			$ 16,439