Segment Information - Geographic Information - Net Sales (Details 4) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Information
Net sales	$ 130,873	$ 132,976	$ 135,452	$ 135,703	$ 140,640	$ 137,699	$ 145,132	$ 131,632	$ 535,004	$ 555,103	$ 547,939
United States
Segment Information
Net sales									288,645	261,849	272,644
United Kingdom
Segment Information
Net sales									43,217	46,049	40,215
Japan
Segment Information
Net sales									35,753	45,261	60,804
France
Segment Information
Net sales									20,875	28,575	27,969
China
Segment Information
Net sales									17,943	17,166	15,832
Germany
Segment Information
Net sales									17,804	20,656	18,784
Canada
Segment Information
Net sales									17,065	21,910	16,945
South Korea
Segment Information
Net sales									12,218	18,692	7,364
Belgium
Segment Information
Net sales									10,383	11,166	10,690
Singapore
Segment Information
Net sales									9,923	6,418	9,364
Netherlands
Segment Information
Net sales									5,184	5,466	5,283
Denmark
Segment Information
Net sales									4,252	3,978	3,639
Switzerland
Segment Information
Net sales									3,340	4,937	5,334
Spain
Segment Information
Net sales									3,302	4,049	3,806
Thailand
Segment Information
Net sales									3,290	1,682	1,023
Other
Segment Information
Net sales									$ 41,810	$ 57,249	$ 48,243