Segment Information (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net sales and long-lived assets by geographical area
Net sales	$ 130,732,000	$ 162,366,000	$ 177,812,000	$ 132,536,000	$ 119,606,000	$ 146,447,000	$ 165,614,000	$ 123,820,000	$ 603,446,000	$ 555,487,000	$ 526,544,000
Long-Lived Assets	205,179,000				194,199,000				205,179,000	194,199,000	200,990,000
Largest customer | Net sales
Net sales and long-lived assets by geographical area
Percentage of net sales attributable to largest customer	10.00%				11.00%				10.00%	11.00%	12.00%
United States
Net sales and long-lived assets by geographical area
Net sales									433,242,000	401,675,000	393,078,000
Long-Lived Assets	165,363,000				154,182,000				165,363,000	154,182,000	157,228,000
Long-lived assets sold					12,000,000					12,000,000
Canada
Net sales and long-lived assets by geographical area
Net sales									42,350,000	43,165,000	34,121,000
Long-Lived Assets	5,964,000				6,117,000				5,964,000	6,117,000	5,818,000
Denmark
Net sales and long-lived assets by geographical area
Net sales									20,162,000	18,623,000	18,893,000
Long-Lived Assets	2,831,000				3,533,000				2,831,000	3,533,000	4,658,000
United Kingdom
Net sales and long-lived assets by geographical area
Net sales									23,598,000	20,233,000	18,157,000
Long-Lived Assets	1,370,000				1,660,000				1,370,000	1,660,000	2,150,000
France
Net sales and long-lived assets by geographical area
Net sales									43,319,000	34,552,000	31,897,000
Long-Lived Assets	10,530,000				12,573,000				10,530,000	12,573,000	13,634,000
Germany
Net sales and long-lived assets by geographical area
Net sales									27,237,000	24,221,000	21,269,000
Long-Lived Assets	4,957,000				1,278,000				4,957,000	1,278,000	1,434,000
Ireland
Net sales and long-lived assets by geographical area
Net sales									2,720,000	2,769,000	2,552,000
Long-Lived Assets	3,075,000				3,454,000				3,075,000	3,454,000	3,993,000
China/Hong Kong
Net sales and long-lived assets by geographical area
Net sales									4,754,000	5,027,000	2,890,000
Long-Lived Assets	10,022,000				10,522,000				10,022,000	10,522,000	11,105,000
Australia
Net sales and long-lived assets by geographical area
Net sales									4,774,000	4,205,000	2,610,000
Long-Lived Assets	507,000				276,000				507,000	276,000	344,000
Other countries
Net sales and long-lived assets by geographical area
Net sales									1,290,000	1,017,000	1,077,000
Long-Lived Assets	$ 560,000				$ 604,000				$ 560,000	$ 604,000	$ 626,000