Selected Quarterly Financial Data (Details) (USD $)	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
Quarterly Financial Information Disclosure [Abstract]
Deferred Tax Benefit Expense Valuation Allowance Adj Capital Loss Carryforwards	$ 4,800,000								$ 4,900,000
Sales	239,219,000	240,429,000	236,965,000	235,213,000	231,096,000	243,194,000	243,530,000	241,526,000	951,826,000		959,346,000		882,188,000
Gross profit	34,109,000	34,582,000	38,480,000	37,749,000	34,417,000	37,253,000	37,540,000	36,836,000
Income from continuing operations	13,054,000	10,745,000	3,752,000	8,479,000	9,402,000	7,428,000	9,590,000	9,517,000	36,029,000		35,937,000		43,185,000
Income (loss) from discontinued operations	0	850,000	0	0	0	(450,000)	(8,300,000)	(5,240,000)	850,000	[1]	(13,990,000)	[1]	(14,934,000)	[1]
Net income (loss)	13,054,000	11,595,000	3,752,000	8,479,000	9,402,000	6,978,000	1,290,000	4,277,000	36,879,000		21,947,000		28,251,000
Basic:
Continuing operations	$ 0.40	$ 0.33	$ 0.12	$ 0.26	$ 0.29	$ 0.23	$ 0.30	$ 0.30	$ 1.12		$ 1.12		$ 1.35
Discontinued operations	$ 0.00	$ 0.03		$ 0.00	$ 0.00	$ (0.01)	$ (0.26)	$ (0.16)	$ 0.02		$ (0.44)		$ (0.47)
Net income	$ 0.40	$ 0.36	$ 0.12	$ 0.26	$ 0.29	$ 0.22	$ 0.04	$ 0.14	$ 1.14		$ 0.68		$ 0.88
Diluted:
Continuing operations (in usd per share)	$ 0.40	$ 0.33	$ 0.11	$ 0.26	$ 0.29	$ 0.23	$ 0.29	$ 0.29	$ 1.11		$ 1.10		$ 1.34
Discontinued operations (in usd per share)	$ 0.00	$ 0.03		$ 0.00	$ 0.00	$ (0.02)	$ (0.25)	$ (0.16)	$ 0.02		$ (0.43)		$ (0.46)
Net income (in usd per share)	$ 0.40	$ 0.36	$ 0.11	$ 0.26	$ 0.29	$ 0.21	$ 0.04	$ 0.13	$ 1.13		$ 0.67		$ 0.88
Shares used to compute earnings (loss) per share:
Shares used to compute earnings (loss) per share, Basic (in shares)	32,335,000	32,319,000	32,312,000	32,242,000	32,222,000	32,201,000	32,187,000	32,076,000	32,302,108		32,171,751		32,032,343
Shares used to compute earnings (loss) per share, Diluted (in shares)	32,449,000	32,507,000	32,641,000	32,621,000	32,622,000	32,658,000	32,635,000	32,480,000	32,553,854		32,599,279		32,192,576
Deferred Tax Benefit Expense Unremitted Earnings FCTA									$ 2,200,000

[1] See Notes 1, 3, 4 and 18 for more information on losses associated with plant shutdowns, asset impairments and restructurings, unusual items, gains or losses from sale of assets, gains or losses on an investment accounted for under the fair value method and other items.