QUARTERLY FINANCIAL DATA - UNAUDITED (Details) (USD $)	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
QUARTERLY FINANCIAL DATA - UNAUDITED
Net sales	$ 133,092,000	$ 139,375,000	$ 140,432,000	$ 135,040,000	$ 141,777,000	$ 135,467,000	$ 148,403,000	$ 136,608,000	$ 547,939,000	$ 562,255,000	$ 541,472,000
Net sales less cost of products sold (excluding depreciation)	45,603,000	46,374,000	46,375,000	42,625,000	44,221,000	36,923,000	45,947,000	42,782,000
Net income (loss)	11,044,000	11,885,000	12,970,000	9,814,000	9,103,000	(4,453,000)	10,884,000	7,738,000
Basic:
Basic net income (loss) per common share (in dollars per share)	$ 0.20	$ 0.22	$ 0.24	$ 0.18	$ 0.16	$ (0.08)	$ 0.19	$ 0.14	$ 0.85	$ 0.41	$ 0.70
Diluted:
Diluted net income (loss) per common share (in dollars per share)	$ 0.20	$ 0.22	$ 0.24	$ 0.18	$ 0.16	$ (0.08)	$ 0.19	$ 0.14	$ 0.84	$ 0.41	$ 0.69
Average common shares outstanding
Basic (in shares)	54,265,000	53,900,000	53,799,000	53,620,000	55,390,000	56,682,000	56,639,000	56,512,000	53,897,834	56,304,636	56,243,015
Diluted (in shares)	55,160,000	54,764,000	54,547,000	54,200,000	55,837,000	57,197,000	57,190,000	57,124,000	54,671,029	56,835,560	56,993,948
Restructuring charges					2,200,000	8,000,000			(129,000)	10,211,000
Multi-employer plan charge						1,700,000
Amount related to an agreement with former Chief Executive Officer included in quarterly financial data						$ 1,700,000