Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Statement Of Cash Flows [Abstract]
Net cash flows (used in) provided by operating activities	$ (707)	$ 10,092
Cash flows from investing activities:
Purchases of property, plant and equipment	(2,840)	(4,562)
Purchases of long-term marketable securities	(210)	(163)
Proceeds from the sale of long-term marketable securities	183	140
Proceeds from the disposition of property, plant and equipment	0	6
Net cash flows used in investing activities	(2,867)	(4,579)
Cash flows from financing activities:
Dividends paid	(1,867)	(1,862)
Net cash flows used in financing activities	(1,867)	(1,862)
Effect of exchange rate changes on cash and cash equivalents	125	(375)
Net (decrease) increase in cash and cash equivalents	(5,316)	3,276
Cash and cash equivalents at beginning of period	97,910	78,889
Cash and cash equivalents at end of period	92,594	82,165
Supplemental information:
Income tax payments	3,018	0
Interest payments	54	54
Non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 997	$ 812