Accounts Receivable, net - Summary of accounts receivable, net (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable [Abstract]
Accounts receivable-net	$ 26,219	$ 30,077
Government
Accounts Receivable [Abstract]
Accounts receivable-net	8,537	7,051
Government \| Billed
Accounts Receivable [Abstract]
Accounts receivable-net	9,100	9,028
Government \| Advanced billings
Accounts Receivable [Abstract]
Accounts receivable-net	(563)	(1,977)
Restaurant/Retail
Accounts Receivable [Abstract]
Accounts receivable-net	$ 17,682	$ 23,026

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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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