Consolidated Quarterly Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly financial data
Net Sales	$ 195,140	$ 188,541	$ 200,238	$ 168,092	$ 187,507	$ 178,268	$ 199,493	$ 173,712	$ 752,011	$ 738,980	$ 753,998
Gross Profit	83,782	81,862	87,741	72,523	83,463	77,563	88,951	75,319	325,908	325,296	319,181
Net Earnings	$ 10,301	$ 10,617	$ 14,254	$ 5,059	$ 13,844	$ 8,745	$ 13,671	$ 5,324	$ 40,231	$ 41,584	$ 32,713
Earnings Per Share, Basic	$ 0.56	$ 0.58	$ 0.78	$ 0.28	$ 0.75	$ 0.47	$ 0.74	$ 0.28	$ 2.20	$ 2.24	$ 1.74
Earnings Per Share, Diluted	$ 0.55	$ 0.56	$ 0.76	$ 0.27	$ 0.73	$ 0.46	$ 0.71	$ 0.28	$ 2.14	$ 2.18	$ 1.69
Cash Dividends Declared per Common Share	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.17	$ 0.17	$ 0.17	$ 0.72	$ 0.69	$ 0.68