Accounts Receivable, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for doubtful accounts	$ 149	$ 453	$ 648
Hardware and other revenue
Accounts, Notes, Loans and Financing Receivable [Line Items]
Reserve for product returns	$ 300	$ 2,100	$ 2,100