Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 73,757	$ 90,635
Trade accounts and other receivables, net	156,138	103,258
Inventories:
Finished goods	83,159	102,625
Raw materials and supplies	46,386	38,061
Total inventories	129,545	140,686
Prepaid expenses and other current assets	8,077	4,293
Deferred income taxes	10,745	11,045
Total current assets	378,262	349,917
Property, plant and equipment:
Land and land improvements	24,561	19,700
Land-use and mineral rights	11,156	9,559
Buildings	70,256	67,866
Machinery and equipment	532,533	530,129
Construction in progress	85,709	39,564
Total	724,215	666,818
Less accumulated depreciation and amortization	272,163	240,586
Net property, plant and equipment	452,052	426,232
Goodwill	12,164	12,164
Intangible and other assets, net	18,076	20,565
Total assets	860,554	808,878
Current liabilities:
Accounts payable	22,674	20,078
Accrued income taxes	2,185	727
Accrued freight	7,865	4,925
Dividends payable	6,924
Other accrued expenses	26,162	25,100
Total current liabilities	65,810	50,830
Deferred income taxes	47,918	44,970
Shareholders' equity:
Preferred stock, par value $0.01 per share, 5,000 shares authorized, none outstanding
Common stock, par value $0.01 per share, 80,000,000 shares authorized; 23,080,505 and 23,092,906 shares issued and outstanding at September 30, 2013 and December 31, 2012, respectively	231	231
Additional paid-in capital	55,533	57,364
Retained earnings	694,115	657,423
Accumulated other comprehensive loss	(3,053)	(1,940)
Total shareholders' equity	746,826	713,078
Total liabilities and shareholders' equity	$ 860,554	$ 808,878