Supplemental Quarterly Financial Data (Unaudited) - Prior Period Balance Sheet Adjustments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2013	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets
Total Current Assets	$ 328,741	$ 338,206	$ 336,713	$ 327,361	$ 333,581	$ 327,366	$ 333,136	$ 321,122
Total Assets	747,599	754,307	757,297	751,293	762,645	758,742	769,528	762,546
Liabilities
Total current liabilities	111,071	101,896	105,337	97,450	108,258	96,317	106,944	98,620
Total liabilities	491,029	501,189	509,404	511,299	528,374	522,181	542,593	542,520
Equity
Total shareholders’ equity	256,570	253,118	247,893	239,994	234,271	236,561	226,935	220,026	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
As Reported
Assets
Total Current Assets		335,199	334,299	324,859	330,764	324,299	332,063	319,813
Total Assets		755,671	759,254	753,162	764,199	760,046	772,826	765,608
Liabilities
Total current liabilities		98,025	101,748	93,626	103,589	92,017	102,289	93,567
Total liabilities		498,118	506,615	508,275	524,505	518,802	538,859	538,388
Equity
Total shareholders’ equity		257,553	252,639	244,887	239,694	241,244	233,967	227,220
Total liabilities and shareholders’ equity		$ 755,671	$ 759,254	$ 753,162	$ 764,199	$ 760,046	$ 772,826	$ 765,608