Plant Closure (Details) (USD $)	3 Months Ended		9 Months Ended			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Facility closing	Mar. 31, 2013 Facility closing	Sep. 30, 2013 Facility closing	Dec. 31, 2012 Facility closing	Sep. 30, 2013 Facility closing Maximum	Dec. 31, 2012 Facility closing Land and building	Sep. 30, 2013 Facility closing Operating expenses
Plant Closure
Net book value of the long-lived assets, including land, building and equipment	$ 209,641,000	$ 211,132,000	$ 209,641,000	$ 211,132,000	$ 213,452,000	$ 1,700,000		$ 1,700,000	$ 2,800,000		$ 2,700,000
Impairment loss on assets held and in use							1,000,000
Sales of assets			1,823,000	6,937,000		1,000,000
Loss on sales of assets	631,000	33,000	634,000	42,000		700,000
Net book value of remaining equipments to be sold, transferred or scrapped					593,000	100,000		100,000
Severance costs								0	3,000,000
Severance costs paid								300,000	2,400,000
Severance costs reversed								200,000
Severance costs accrued									600,000
Severance costs to be paid in 2014										100,000
Estimated closure costs								100,000				500,000
Plant closure expenses								100,000	300,000
Plant closure expenses paid								200,000	200,000
Plant closure expenses to be paid in 2013									$ 100,000