Operations and Summary of Significant Accounting Policies (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 series item	Dec. 31, 2011	Dec. 31, 2010
Plant Closure
Net book value of the long-lived assets, including land, building and equipment	$ 213,452,000				$ 195,716,000				$ 213,452,000	$ 195,716,000
Additional depreciation									19,000,000	16,300,000	16,800,000
Common Stock
Number of votes for each share of common stock held									1
Number of rights per common stock as a part of dividend distribution									1
Percentage acquisition of common stock triggering exercise terms of rights, minimum									15.00%
Ownership interest held by any stockholder at date of rights distribution to which additional exercise terms for the Rights distributed apply (as a percent)									25.00%
Subsequent increase in ownership interest held by any stockholder after rights distribution to which additional exercise terms for the Rights distributed apply (as a percent)									40.00%
Redemption price per right (in cents per right)									$ 0.01
Preferred Stock
Number of series by which the Board may issue authorized and unissued preferred stock, minimum									1
Preferred stock designated as Series A Participating and reserved for issuance on exercise of the Rights	1,000,000								1,000,000
Number of banks where demand deposit or money market accounts are held by the company									10
Reconciliation of basic earnings per share ("EPS") to diluted EPS
Earnings from continuing operations, net of tax					4,948,000	19,380,000	19,493,000	7,078,000	41,918,000	50,900,000	44,798,000
Loss from discontinued operations, net of tax											(16,212,000)
Net income	5,883,000	12,976,000	15,859,000	7,201,000	4,948,000	19,380,000	19,493,000	7,078,000	41,918,000	50,900,000	28,586,000
Basic weighted average shares outstanding									48,339,000	48,974,000	49,498,000
Dilutive effect of potential common stock equivalents - stock options (in shares)									73,000	49,000	114,000
Diluted weighted average shares outstanding									48,412,000	49,023,000	49,612,000
Earnings per common share - basic:
Continuing operations (in dollars per share)									$ 0.87	$ 1.04	$ 0.91
Discontinued operations (in dollars per share)											$ (0.33)
Net income (in dollars per share)	$ 0.12	$ 0.27	$ 0.33	$ 0.15	$ 0.10	$ 0.40	$ 0.39	$ 0.14	$ 0.87	$ 1.04	$ 0.58
Earnings per common share - diluted:
Continuing operations (in dollars per share)									$ 0.87	$ 1.04	$ 0.90
Discontinued operations (in dollars per share)											$ (0.33)
Net income (in dollars per share)	$ 0.12	$ 0.27	$ 0.33	$ 0.15	$ 0.10	$ 0.40	$ 0.39	$ 0.14	$ 0.87	$ 1.04	$ 0.58
Potentially dilutive securities excluded from earnings per diluted share because their effect is anti-dilutive (in shares)									1,700,000	1,363,000	1,018,000
Comprehensive Income
Translation adjustments, net of tax	12,342,000				6,783,000				12,342,000	6,783,000
Unamortized pension adjustments, net of tax	(243,000)								(243,000)
Total accumulated other comprehensive income	12,099,000				6,783,000				12,099,000	6,783,000
Translation adjustments, tax	883,000				916,000				883,000	916,000
Unamortized pension adjustments, tax benefit									46,000
Concentration of Credit Risk
Number of banks where demand deposit or money market accounts are held by the company									10
Facility closing
Plant Closure
Severance costs									3,000,000
Severance costs paid									2,400,000
Severance costs to be paid in 2013									600,000
Net book value of the long-lived assets, including land, building and equipment	2,800,000								2,800,000
Additional depreciation									200,000
Plant closing expenses									300,000
Plant closing expenses paid									200,000
Plant closing expenses to be paid in 2013									100,000
Estimated additional closing costs to be incurred and paid in 2013									400,000
Amount of assets sold									1,600,000
Facility closing | Cost of sales
Plant Closure
Severance costs									2,300,000
Loss on sale of inventory									1,000,000
Facility closing | Operating expenses
Plant Closure
Severance costs									700,000
Estimated closing costs									700,000
Accelerated amortization									$ 600,000