Detail of Selected Balance Sheet Accounts (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in the inventory reserves [Roll Forward]
Balance at beginning of year	$ 3,709	$ 3,925	$ 4,366
Provision for inventory write-downs	515	615	34
Deduction for inventory write-offs	(640)	(831)	(475)
Balance at end of year	$ 3,584	$ 3,709	$ 3,925