Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Prior Period Adjustments (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2013	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Jun. 28, 2014	Jun. 29, 2013	Sep. 27, 2014	Sep. 28, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred income taxes				$ (604)				$ (1,883)	$ 998	$ 1,868	$ 2,073	$ 833	$ 345	$ (1,551)	$ 1,098
Inventories				(8,388)				(993)	(1,694)	(357)	(4,961)	(1,055)	(2,335)	6,962	5,870
Assets
Total Current Assets	328,741	338,206	336,713	327,361	333,581	327,366	333,136	321,122	336,713	333,136	338,206	327,366	328,741	333,581
Total Assets	747,599	754,307	757,297	751,293	762,645	758,742	769,528	762,546	757,297	769,528	754,307	758,742	747,599	762,645
Liabilities
Total current liabilities	111,071	101,896	105,337	97,450	108,258	96,317	106,944	98,620	105,337	106,944	101,896	96,317	111,071	108,258
Total liabilities	491,029	501,189	509,404	511,299	528,374	522,181	542,593	542,520	509,404	542,593	501,189	522,181	491,029	528,374
Equity
Total Shareholders’ Equity	256,570	253,118	247,893	239,994	234,271	236,561	226,935	220,026	247,893	226,935	253,118	236,561	256,570	234,271	215,217	195,640
Total Liabilities and Shareholders’ Equity	747,599	754,307	757,297	751,293	762,645	758,742	769,528	762,546	757,297	769,528	754,307	758,742	747,599	762,645
Net Income
Gross profit	33,627	33,112	37,678	35,915	19,565	33,739	37,574	33,274	73,593	70,848	106,705	104,587	140,332	124,152	143,977
Operating income		10,062	16,810	14,828		13,388	15,301	10,723	31,638	26,024	41,700	39,412	51,767	39,303	56,922
Net Income	5,156	2,933	6,619	5,159	(5,244)	6,985	5,666	3,971	11,778	9,637	14,711	16,622	19,867	11,378	17,623
Earnings Per Share
Basic (in dollars per share)	$ 0.47	$ 0.27	$ 0.61	$ 0.48	$ (0.49)	$ 0.65	$ 0.53	$ 0.37	$ 1.08	$ 0.91	$ 1.35	$ 1.56	$ 1.82	$ 1.06	$ 1.67
Diluted (in dollars per share)	$ 0.46	$ 0.26	$ 0.60	$ 0.46	$ (0.49)	$ 0.64	$ 0.53	$ 0.37	$ 1.06	$ 0.90	$ 1.31	$ 1.54	$ 1.79	$ 1.05	$ 1.66
Cash Flows from Operating Activities
Net Income	5,156	2,933	6,619	5,159	(5,244)	6,985	5,666	3,971	11,778	9,637	14,711	16,622	19,867	11,378	17,623
Other assets				(5,440)				(1,456)	(6,563)	3,473	(6,633)	10,482	(4,800)	12,173	(6,829)
Accrued and other liabilities				(6,067)				(12,386)	835	(3,775)	(5,400)	(12,819)	6,103	(9,153)	(4,892)
As Reported
Deferred income taxes				(919)				(2,040)	595	1,615	1,775	45		(2,242)	(142)
Inventories				(8,388)				(1,084)	(1,694)	(588)	(4,961)	(206)		7,811	6,185
Assets
Total Current Assets		335,199	334,299	324,859	330,764	324,299	332,063	319,813	334,299	332,063	335,199	324,299		330,764
Total Assets		755,671	759,254	753,162	764,199	760,046	772,826	765,608	759,254	772,826	755,671	760,046		764,199
Liabilities
Total current liabilities		98,025	101,748	93,626	103,589	92,017	102,289	93,567	101,748	102,289	98,025	92,017		103,589
Total liabilities		498,118	506,615	508,275	524,505	518,802	538,859	538,388	506,615	538,859	498,118	518,802		524,505
Equity
Total Shareholders’ Equity		257,553	252,639	244,887	239,694	241,244	233,967	227,220	252,639	233,967	257,553	241,244		239,694
Total Liabilities and Shareholders’ Equity		755,671	759,254	753,162	764,199	760,046	772,826	765,608	759,254	772,826	755,671	760,046		764,199
Net Income
Gross profit		33,394	37,443	35,070		32,304	37,316	32,853	72,513	70,169	105,907	102,473		122,417	141,452
Operating income		10,344	16,575	13,983		11,953	15,043	10,302	30,558	25,345	40,902	37,298		37,568	54,813
Net Income		2,622	6,472	4,629		4,636	5,504	3,707	11,101	9,211	13,723	13,847		9,343	16,437
Earnings Per Share
Basic (in dollars per share)		$ 0.24	$ 0.60	$ 0.43		$ 0.43	$ 0.52	$ 0.35	$ 1.02	$ 0.87	$ 1.26	$ 1.30		$ 0.87	$ 1.55
Diluted (in dollars per share)		$ 0.24	$ 0.59	$ 0.42		$ 0.42	$ 0.51	$ 0.35	$ 1.00	$ 0.86	$ 1.23	$ 1.28		$ 0.86	$ 1.55
Cash Flows from Operating Activities
Net Income		2,622	6,472	4,629		4,636	5,504	3,707	11,101	9,211	13,723	13,847		9,343	16,437
Other assets				(5,440)				(1,456)	(6,563)	3,473	(7,121)	9,033		11,192	(6,846)
Accrued and other liabilities				$ (6,067)				$ (12,386)	$ 835	$ (3,775)	$ (5,400)	$ (12,819)		$ (9,143)	$ (5,008)