12. Deposits and other assets (Details) - USD ($) $ in Thousands	Dec. 30, 2017	Dec. 31, 2016
Assets, Noncurrent [Abstract]
Deposits	$ 411	$ 232
Other	107	104
Total other assets	$ 518	$ 336

Carrying value of amounts transferred to third parties for security purposes that are expected to be returned or applied towards payment after one year or beyond the operating cycle, if longer.

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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