Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 83,797	$ 90,635
Trade accounts and other receivables, net	109,036	103,258
Inventories:
Finished goods	105,586	102,625
Raw materials and supplies	41,833	38,061
Total inventories	147,419	140,686
Prepaid expenses and other current assets	4,831	4,293
Deferred income taxes	11,192	11,045
Total current assets	356,275	349,917
Property, plant and equipment:
Land and land improvements	19,762	19,700
Land-use and mineral rights	9,566	9,559
Buildings	67,836	67,866
Machinery and equipment	534,146	530,129
Construction in progress	47,295	39,564
Total	678,605	666,818
Less accumulated depreciation and amortization	250,675	240,586
Net property, plant and equipment	427,930	426,232
Goodwill	12,164	12,164
Intangible and other assets, net	19,549	20,565
Total assets	815,918	808,878
Current liabilities:
Accounts payable	18,820	20,078
Accrued income taxes	7,107	727
Dividends payable	6,247
Other accrued expenses	22,380	30,025
Total current liabilities	54,554	50,830
Deferred income taxes	45,929	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; 23,137,052 and 23,092,906 shares issued and outstanding at March 31, 2013 and December 31, 2012, respectively	231	231
Additional paid-in capital	56,087	57,364
Retained earnings	661,509	657,423
Accumulated other comprehensive loss	(2,392)	(1,940)
Total shareholders' equity	715,435	713,078
Total liabilities and shareholders' equity	$ 815,918	$ 808,878