Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Cash Flows [Abstract]
Net cash flows (used in) provided by operating activities	$ (5,039)	$ 2,080
Cash flows from investing activities:
Purchases of property, plant and equipment	(562)	(2,493)
Proceeds from the sale of property, plant and equipment	7	0
Purchase of Åkers, net of cash acquired (Note 2)	(27,031)	0
Purchases of long-term marketable securities	(246)	(39)
Proceeds from the sale of long-term marketable securities	193	20
Net cash flows used in investing activities	(27,639)	(2,512)
Cash flows from financing activities:
Dividends paid	(1,879)	(1,877)
Net cash flows used in financing activities	(1,879)	(1,877)
Effect of exchange rate changes on cash and cash equivalents	(424)	(790)
Net decrease in cash and cash equivalents	(34,981)	(3,099)
Cash and cash equivalents at beginning of period	95,122	97,098
Cash and cash equivalents at end of period	60,141	93,999
Supplemental information:
Income tax payments	3,000	2,772
Interest payments	61	59
Non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	152	656
Non-cash financing activities:
Issuance of common stock to acquire net assets of Åkers (Note 2)	22,137	0
Issuance of debt to acquire net assets of Åkers (Note 2)	$ 25,710	$ 0