Accounts Receivable, net - Summary of accounts receivable, net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts Receivable [Abstract]
Accounts receivable-net	$ 30,077	$ 30,705
Government
Accounts Receivable [Abstract]
Accounts receivable-net	7,051	5,180
Government \| Billed
Accounts Receivable [Abstract]
Accounts receivable-net	9,028	6,779
Government \| Advanced billings
Accounts Receivable [Abstract]
Accounts receivable-net	(1,977)	(1,599)
Restaurant/Retail
Accounts Receivable [Abstract]
Accounts receivable-net	$ 23,026	$ 25,525

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_AccountsReceivableNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant