Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Selected quarterly financial information [Abstract]
Net sales	$ 218,054	$ 257,046	$ 272,540	$ 232,752	$ 218,708	$ 264,162	$ 270,126	$ 230,708	$ 980,392	$ 983,704	$ 948,916
Gross profit	67,094	77,227	77,399	67,910	66,749	80,081	77,796	65,828	289,630	290,454	259,669
Earnings from continuing operations	11,517	17,806	11,169	12,407	9,391	17,686	16,400	9,566	52,899	53,043	42,969
Loss from discontinued operations, net of taxes	(419)	(8,240)	(529)	(682)	(455)	(389)	(357)	(392)	(9,870)	(1,593)	(1,616)
Net earnings	$ 11,098	$ 9,566	$ 10,640	$ 11,725	$ 8,936	$ 17,297	$ 16,043	$ 9,174	$ 43,029	$ 51,450	$ 41,353
Net earnings from continuing operations per common share [Abstract]
Basic (in dollars per share)	$ 0.50	$ 0.78	$ 0.49	$ 0.54	$ 0.41	$ 0.77	$ 0.71	$ 0.42	$ 2.31	$ 2.31	$ 1.88
Diluted (in dollars per share)	$ 0.50	$ 0.77	$ 0.48	$ 0.53	$ 0.40	$ 0.76	$ 0.71	$ 0.41	$ 2.28	$ 2.28	$ 1.86
Net earnings per common share [Abstract]
Basic (in dollars per share)	$ 0.48	$ 0.42	$ 0.47	$ 0.51	$ 0.39	$ 0.75	$ 0.70	$ 0.40	$ 1.88	$ 2.24	$ 1.81
Diluted (in dollars per share)	$ 0.48	$ 0.41	$ 0.46	$ 0.50	$ 0.38	$ 0.74	$ 0.69	$ 0.40	$ 1.85	$ 2.21	$ 1.79