Quarterly Financial Information (Unaudited) (Tables) (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
Net sales	$ 156,458	$ 162,248	$ 149,936	$ 129,321	$ 140,724	$ 170,346	[1]	$ 163,180	[2]	$ 114,291	$ 597,963	$ 588,541	$ 575,337
Gross profit	30,611	31,305	29,175	24,848	27,570	30,713	[1]	12,334	[2]	21,652	115,939	92,269	98,410
Income from continuing operations	7,275	9,793	7,257	4,951	6,643	8,463	[1]	(3,321)	[2]	2,979	29,276	14,764	22,067
Income from discontinued operations			38	(24)	22	(238)	[1]	1,250	[2]	390	14	1,424	828
Net income	7,275	9,793	7,295	4,927	6,665	8,225	[1]	(2,071)	[2]	3,369	29,290	16,188	22,895
Basic earnings per common share: From continuing operations	$ 0.71	$ 0.96	$ 0.71	$ 0.49	$ 0.65	$ 0.83	[1]	$ (0.33)	[2]	$ 0.30	$ 2.88	$ 1.46	$ 2.16
Basic earnings per common share: From discontinued operations			$ 0.00	$ 0.00	$ 0.00	$ (0.02)	[1]	$ 0.12	[2]	$ 0.04	$ 0.00	$ 0.14	$ 0.08
Basic earnings per common share	$ 0.71	$ 0.96	$ 0.72	$ 0.49	$ 0.66	$ 0.81	[1]	$ (0.20)	[2]	$ 0.33	$ 2.88	$ 1.60	$ 2.24
Diluted earnings per common share: From continuing operations	$ 0.71	$ 0.95	$ 0.71	$ 0.48	$ 0.65	$ 0.83	[1]	$ (0.33)	[2]	$ 0.29	$ 2.85	$ 1.44	$ 2.14
Diluted earnings per common share: From discontinued operations			$ 0.00	$ 0.00		$ (0.02)	[1]	$ 0.12	[2]	$ 0.04	$ 0.00	$ 0.14	$ 0.08
Diluted earnings per common share	$ 0.71	$ 0.95	$ 0.71	$ 0.48	$ 0.65	$ 0.81	[1]	$ (0.20)	[2]	$ 0.32	$ 2.85	$ 1.58	$ 2.22
Dividends paid per common share	$ 0.03	$ 0.03	$ 0.03	$ 0.03	$ 0.025	$ 0.025	[1]	$ 0.025	[2]	$ 0.025	$ 0.12	$ 0.10	$ 0.10
Sale Leaseback Transaction, Cumulative Gain Recognized					577							577
Shipping Systems Division [Member]
Significant Acquisitions and Disposals, Gain (Loss) on Sale or Disposal, Pretax								3,508
Precise Structural Products Business [Member]
Significant Acquisitions and Disposals, Gain (Loss) on Sale or Disposal, Pretax						$ (315)

[1] Includes a pre-tax loss of approximately $315 from the Company’s sale of Precise.

[2] Includes a pre-tax gain of approximately $3,508 from the Company’s sale of SSD.