6. Employee Retirement Benefit Plans: Schedule of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 27, 2019	Sep. 28, 2018
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Interest cost	$ 37	$ 35	$ 110	$ 103
Amortization of actuarial loss	20	20	60	60
Net periodic benefit cost	$ 57	$ 55	$ 170	$ 163