Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 segment	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Segment Information
Number of reportable segments			3
Segment Information
Net sales	$ 181,703	$ 177,812	$ 340,437	$ 310,348
Sales to Other Segments	6,034	3,703	11,264	7,217
Income (Loss) from Operations	27,148	31,208	40,656	43,490
Total Assets	878,905	864,575	878,905	864,575	836,087
Cash and short-term investments	162,719	262,013	162,719	262,013	213,817	335,049
North America
Segment Information
Net sales	144,532	139,112	272,500	243,734
Sales to Other Segments	1,442	1,490	2,814	2,812
Income (Loss) from Operations	26,583	30,793	44,456	45,843
Total Assets	557,502	595,842	557,502	595,842	540,082
Europe
Segment Information
Net sales	34,120	35,648	62,356	61,446
Sales to Other Segments	19	169	153	250
Income (Loss) from Operations	2,088	2,650	(284)	1,196
Total Assets	204,864	140,572	204,864	140,572	180,016
Asia/Pacific
Segment Information
Net sales	2,735	2,815	5,107	4,692
Sales to Other Segments	4,573	2,044	8,297	4,155
Income (Loss) from Operations	(163)	(552)	(817)	(1,265)
Total Assets	31,734	25,461	31,734	25,461	29,306
Administrative and all other
Segment Information
Net sales	316	237	474	476
Income (Loss) from Operations	(1,360)	(1,683)	(2,699)	(2,284)
Total Assets	84,805	102,700	84,805	102,700	86,683
Cash and short-term investments	$ 82,600	$ 191,500	$ 82,600	$ 191,500	$ 68,500