2. Revenue: Schedule of contract balances (Details) - USD ($) $ in Thousands	Jun. 28, 2019	Dec. 31, 2018
Text Block [Abstract]
Accounts receivable, net	$ 2,452	$ 3,250
Contract revenue in excess of billings	3,705	3,484
Other Liabilities, Current	$ 3,713	$ 5,959

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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