Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Consolidated Statements of Cash Flows [Abstract]
Net cash flows provided by operating activities	$ 10,092	$ 11,859
Cash flows from investing activities:
Purchases of property, plant and equipment	(4,562)	(2,733)
Purchases of long-term marketable securities	(163)	(179)
Proceeds from the sale of long-term marketable securities	140	153
Proceeds from the disposition of property, plant and equipment	6	0
Net cash flows used in investing activities	(4,579)	(2,759)
Cash flows from financing activities:
Dividends paid	(1,862)	(1,858)
Proceeds from the issuance of common stock	0	78
Excess tax benefits from the exercise of stock options	0	13
Net cash flows used in financing activities	(1,862)	(1,767)
Effect of exchange rate changes on cash and cash equivalents	(375)	502
Net increase in cash and cash equivalents	3,276	7,835
Cash and cash equivalents at beginning of period	78,889	69,888
Cash and cash equivalents at end of period	82,165	77,723
Supplemental information:
Income tax payments	0	997
Interest payments	54	56
Non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 812	$ 692