Basis of Presentation and Significant Accounting Policies (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Inventories Detail [Table]
Finished goods	$ 73,961,000		$ 71,247,000
Raw materials	4,892,000		5,653,000
Parts and supplies	24,434,000		22,216,000
Work in progress	943,000		869,000
Inventories	104,230,000		99,985,000
Weighted Average Shares Outstanding [Table]
Number of weighted average common shares outstanding	77,069,000	76,251,000
Assumed exercise of stock options	1,212,000	0
Average diluted shares outstanding	78,281,000	76,251,000
Average market price of common stock for the period	$ 9.63
Outstanding stock options excluded from average diluted shares outstanding	2,369,632
Fair value of Senior Notes	332,800,000
Carrying value of Senior Notes	$ 305,000,000