Basis of Presentation and Significant Accounting Policies (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Inventories Detail [Table]
Finished goods	$ 69,592,000		$ 69,592,000		$ 71,247,000
Raw materials	4,247,000		4,247,000		5,653,000
Parts and supplies	23,320,000		23,320,000		22,216,000
Work in progress	1,077,000		1,077,000		869,000
Inventories	98,236,000		98,236,000		99,985,000
Weighted Average Shares Outstanding [Table]
Number of weighted average common shares outstanding	77,278,000	76,579,000	77,174,000	76,415,000
Assumed exercise of stock options	1,720,000	1,736,000	1,466,000	1,570,000
Average diluted shares outstanding	78,998,000	78,315,000	78,640,000	77,985,000
Average market price of common stock for the period			$ 8.57
Outstanding stock options excluded from average diluted shares outstanding	3,219,457	1,733,435	2,794,545	1,783,096
Fair value of Senior Notes	329,900,000		329,900,000		332,400,000
Carrying value of Senior Notes	$ 305,000,000		$ 305,000,000