Quarterly Financial Data Unit (Unaudited) (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
Selected quarterly financial information [Abstract]
Net sales	$ 218,708	$ 264,162	$ 270,126	$ 230,708	$ 192,355	$ 275,975	$ 268,875	$ 211,711	$ 983,704	$ 948,916	$ 874,625
Gross profit	66,749	80,081	77,796	65,828	57,967	77,808	69,344	54,550	290,454	259,669	229,147
Earnings from continuing operations	9,391	17,686	16,400	9,566	6,310	17,444	13,721	5,494	53,043	42,969	64,327
Loss on discontinued operations, net of taxes	(455)	(389)	(357)	(392)	(395)	(604)	(317)	(300)	(1,593)	(1,616)	(1,926)
Net earnings	$ 8,936	$ 17,297	$ 16,043	$ 9,174	$ 5,915	$ 16,840	$ 13,404	$ 5,194	$ 51,450	$ 41,353	$ 62,401
Net earnings from continuing operations per common share [Abstract]
Basic (in dollars per share)	$ 0.41	$ 0.77	$ 0.71	$ 0.42	$ 0.28	$ 0.77	$ 0.60	$ 0.24	$ 2.31	$ 1.88	$ 2.82
Diluted (in dollars per share)	$ 0.40	$ 0.76	$ 0.71	$ 0.41	$ 0.27	$ 0.76	$ 0.59	$ 0.24	$ 2.28	$ 1.86	$ 2.78
Net earnings per common share [Abstract]
Basic (in dollars per share)	$ 0.39	$ 0.75	$ 0.70	$ 0.40	$ 0.26	$ 0.74	$ 0.59	$ 0.23	$ 2.24	$ 1.81	$ 2.74
Diluted (in dollars per share)	$ 0.38	$ 0.74	$ 0.69	$ 0.40	$ 0.26	$ 0.74	$ 0.58	$ 0.22	$ 2.21	$ 1.79	$ 2.70