SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts Receivable Reserves
Balance at beginning of period	$ 1,243	$ 1,109	$ 1,630
Charged to cost and expenses	1,126	1,244	2,173
Write-offs, Exchange Rate Fluctuations and Other Items	(1,080)	(1,110)	(2,694)
Balance at end of period	1,289	1,243	1,109
Valuation Allowance Of Deferred Tax Assets [Member]
Balance at beginning of period	8,962	11,986	11,125
Net additions charged to income (expense)	(138)	(1,922)	874
Write-offs, Exchange Rate Fluctuations and Other Items	(238)	(1,102)	(13)
Balance at end of period	$ 8,586	$ 8,962	$ 11,986