Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2011 USD ($)
Segment Information
Number of reportable segments | segment									3
Net sales	$ 184,764	$ 216,139	$ 216,665	$ 176,491	$ 166,630	$ 209,320	$ 207,893	$ 168,305	$ 794,059	$ 752,148	$ 705,322
Income from operations	22,485	35,249	35,009	16,277	15,320	32,218	32,133	19,605	109,021	99,276	81,478
Depreciation and amortization									26,821	27,918	27,518
Impairment of Long-Lived Assets to be Disposed of									0	0	1,025
Significant non-cash charges									11,958	13,190	12,747
Provision for (benefit from) income taxes	7,675	$ 13,479	$ 13,446	$ 6,191	4,942	$ 11,577	$ 11,667	$ 7,605	40,791	35,791	30,593
Capital expenditures and asset acquisitions, net of cash acquired									38,365	23,935	23,297
Total assets	961,309				973,065				961,309	973,065	956,525
Cash and short-term investments	258,825				260,307				$ 258,825	260,307	251,208	$ 175,553
Administrative and all other
Segment Information
Lease term of entity's facilities in Vacaville									10 years
Net sales									$ 0	0	0
Income from operations									(775)	949	(2,463)
Depreciation and amortization									1,451	1,480	1,293
Impairment of Long-Lived Assets to be Disposed of										0	0
Significant non-cash charges									2,355	2,101	2,177
Provision for (benefit from) income taxes									1,519	2,185	1,416
Capital expenditures and asset acquisitions, net of cash acquired									27	0	9
Total assets	20,397				83,664				20,397	83,664	96,385
Cash and short-term investments	164,100				167,400				164,100	167,400	156,000
Intersegment elimination
Segment Information
Net sales									24,284	23,237	21,421
North America
Segment Information
Net sales									676,618	613,843	572,789
Income from operations									109,446	94,888	84,885
Depreciation and amortization									17,812	18,129	17,707
Impairment of Long-Lived Assets to be Disposed of										0	0
Significant non-cash charges									8,221	9,722	8,867
Provision for (benefit from) income taxes									36,999	30,287	26,372
Capital expenditures and asset acquisitions, net of cash acquired									33,336	20,160	19,424
Total assets	748,241				679,844				748,241	679,844	627,196
North America | Intersegment elimination
Segment Information
Net sales									2,857	4,134	4,735
Europe
Segment Information
Net sales									108,068	123,177	117,740
Income from operations									3,795	5,005	1,258
Depreciation and amortization									5,773	6,755	7,019
Impairment of Long-Lived Assets to be Disposed of										530	1,025
Significant non-cash charges									1,251	1,164	1,561
Provision for (benefit from) income taxes									1,692	2,437	2,906
Capital expenditures and asset acquisitions, net of cash acquired									4,177	2,977	2,244
Total assets	168,305				180,005				168,305	180,005	201,384
Europe | Intersegment elimination
Segment Information
Net sales									931	1,170	352
Asia/Pacific
Segment Information
Net sales									9,373	15,128	14,793
Income from operations									(3,445)	(1,566)	(2,202)
Depreciation and amortization									1,785	1,554	1,499
Impairment of Long-Lived Assets to be Disposed of										0	0
Significant non-cash charges									131	203	142
Provision for (benefit from) income taxes									581	882	(101)
Capital expenditures and asset acquisitions, net of cash acquired									825	798	1,620
Total assets	24,366				$ 29,552				24,366	29,552	31,560
Asia/Pacific | Intersegment elimination
Segment Information
Net sales									20,496	$ 17,933	$ 16,334
Foreign operating entities
Segment Information
Cash and short-term investments	$ 93,200								$ 93,200
Percentage of cash and cash equivalents	36.00%								36.00%