Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation and Qualifying Accounts Disclosure
Balance at beginning of year		$ 3,241
Balance at end of year		2,516	$ 3,241
Allowance for Doubtful Accounts and Returns
Valuation and Qualifying Accounts Disclosure
Balance at beginning of year		2,428	2,570	$ 2,929
Charged to costs and expenses		375	1,183	649
Reclassification	[1]	772	(526)	0
Charged to other accounts	[2]	(222)	80	(4)
Deductions	[3]	(837)	(879)	(1,004)
Balance at end of year		2,516	2,428	2,570
Sales Returns and Allowances
Valuation and Qualifying Accounts Disclosure
Balance at beginning of year		813	538	686
Charged to costs and expenses		688	419	(88)
Charged to other accounts	[2]	10	31	(15)
Deductions	[3]	(198)	(175)	(45)
Balance at end of year		1,313	813	538
Inventory Reserves
Valuation and Qualifying Accounts Disclosure
Balance at beginning of year		4,107	3,644	3,540
Charged to costs and expenses		1,916	1,698	1,455
Charged to other accounts	[2]	(139)	183	(50)
Deductions	[4]	(246)	(1,418)	(1,301)
Balance at end of year		5,638	4,107	3,644
Valuation Allowance for Deferred Tax Assets
Valuation and Qualifying Accounts Disclosure
Balance at beginning of year		9,691	6,865	5,884
Charged to costs and expenses		2,373	1,634	1,295
Charged to other accounts	[2]	(545)	1,192	(314)
Balance at end of year		$ 11,519	$ 9,691	$ 6,865

[1] Includes amount reclassified between Allowance for Doubtful Accounts and Other Receivables related to a customer's open receivables balance which was resolved in 2018, as well as acquisition-related adjustments.

[2] Primarily includes impact from foreign currency fluctuations

[3] Includes accounts determined to be uncollectible and charged against reserves, net of collections on accounts previously charged against reserves.

[4] Includes inventory identified as excess, slow moving or obsolete and charged against reserves.