Basis of Presentation and Significant Accounting Policies (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Inventories Detail [Table]
Finished goods	$ 71,703,000		$ 71,703,000		$ 71,247,000
Raw materials	5,051,000		5,051,000		5,653,000
Parts and supplies	24,195,000		24,195,000		22,216,000
Work in progress	1,100,000		1,100,000		869,000
Inventories	102,049,000		102,049,000		99,985,000
Weighted Average Shares Outstanding [Table]
Number of weighted average common shares outstanding	77,329,000	76,717,000	77,226,000	76,517,000
Assumed exercise of stock options	1,609,000	1,623,000	1,514,000	1,588,000
Average diluted shares outstanding	78,938,000	78,340,000	78,740,000	78,105,000
Average market price of common stock for the period			$ 7.96
Outstanding stock options excluded from average diluted shares outstanding	2,144,779	2,054,303	2,576,375	1,874,492
Fair value of Senior Notes	334,100,000		334,100,000		332,400,000
Carrying value of Senior Notes	$ 305,000,000		$ 305,000,000		$ 305,000,000