Consolidated Quarterly Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly financial data
Net Sales	$ 187,507	$ 178,268	$ 199,493	$ 173,712	$ 193,158	$ 186,990	$ 201,259	$ 172,591	$ 738,980	$ 753,998	$ 667,667
Gross Profit	83,463	77,563	88,951	75,319	83,529	80,253	83,468	71,931	325,296	319,181	284,326
Net Earnings	$ 13,844	$ 8,745	$ 13,671	$ 5,324	$ 11,264	$ 9,728	$ 5,855	$ 5,866	$ 41,584	$ 32,713	$ 34,803
Earnings Per Share, Basic	$ 0.75	$ 0.47	$ 0.74	$ 0.28	$ 0.60	$ 0.52	$ 0.31	$ 0.31	$ 2.24	$ 1.74	$ 1.85
Earnings Per Share, Diluted	$ 0.73	$ 0.46	$ 0.71	$ 0.28	$ 0.59	$ 0.50	$ 0.30	$ 0.30	$ 2.18	$ 1.69	$ 1.80
Cash Dividends Declared per Common Share	$ 0.18	$ 0.17	$ 0.17	$ 0.17	$ 0.17	$ 0.17	$ 0.17	$ 0.17	$ 0.69	$ 0.68	$ 0.59