Business Acquisition - Allocation of Total Purchase Consideration (Details) - USD ($) $ in Thousands	Nov. 03, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill		$ 25,894	$ 25,894	$ 25,894
Evolv Inc.
Business Acquisition [Line Items]
Cash and cash equivalents	$ 107
Account receivables	979
Prepaid expenses and other current assets	194
Property and equipment	77
Intangibles - Developed technology	26,184
Goodwill	17,701
Total assets acquired	45,242
Accounts payable	712
Accrued expenses	619
Deferred revenue	477
Total liabilities assumed	1,808
Total purchase price	$ 43,434