Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 segment	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Segment Information
Number of reportable segments			3
Segment Information
Net sales	$ 195,877	$ 172,113	$ 546,008	$ 512,550
Income (loss) from operations	30,885	21,990	69,575	62,647
Total Assets	934,176	878,996	934,176	878,996	890,322
Cash and cash equivalent	215,764	187,471	215,764	187,471	175,553	213,817
Administrative and all other
Segment Information
Net sales	237	237	712	712
Income (loss) from operations	(807)	(241)	(3,871)	(2,940)
Total Assets	74,002	82,168	74,002	82,168	82,366
Cash and cash equivalent	120,100	107,300	120,100	107,300	91,900
Intersegment elimination
Segment Information
Net sales	5,304	4,968	16,558	16,232
North America
Segment Information
Net sales	157,278	137,145	444,772	409,644
Income (loss) from operations	28,659	22,102	73,582	66,558
Total Assets	630,459	568,878	630,459	568,878	583,501
North America | Intersegment elimination
Segment Information
Net sales	1,316	969	3,247	3,783
Europe
Segment Information
Net sales	33,887	31,880	89,903	94,236
Income (loss) from operations	3,682	1,172	1,742	889
Total Assets	196,958	196,883	196,958	196,883	194,000
Europe | Intersegment elimination
Segment Information
Net sales	20	105	332	258
Asia/Pacific
Segment Information
Net sales	4,475	2,851	10,621	7,958
Income (loss) from operations	(649)	(1,043)	(1,878)	(1,860)
Total Assets	32,757	31,067	32,757	31,067	30,455
Asia/Pacific | Intersegment elimination
Segment Information
Net sales	$ 3,968	$ 3,894	$ 12,979	$ 12,191