Changes in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance For Doubtful Accounts Receivable Rollforward
Balance at beginning of year	$ 500	$ 282	$ 575
Provision charged to selling, general and administrative expenses	135	285	30
Allowance resulting from acquisitions	15	5	52
Write-offs, net of recoveries of amounts previously reserved	(82)	(29)	(352)
Divestiture of JK Lasers		(30)
Exchange rate changes	(3)	(13)	(23)
Balance at end of year	$ 565	$ 500	$ 282