Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets
Cash and cash equivalents	$ 591,556	$ 790,078
Marketable Securities, Current	125,597	124,873
Accounts receivable, net	433,025	400,159
Inventories	451,571	399,298
Prepaid expenses and other current assets	18,809	14,700
Deferred income taxes	22,293	22,305
Total current assets	1,642,851	1,751,413
Property, plant and equipment, net	1,952,918	1,510,048
Equity investments	65,488	43,736
Other assets, net
Intangible assets, net	159,376	48,292
Deferred charges and other assets	102,816	58,707
Total other assets, net	262,192	106,999
Total assets	3,923,449	3,412,196
Current liabilities
Accounts payable	258,067	217,050
Accrued liabilities	174,619	181,460
Total current liabilities	432,686	398,510
Long-term debt	763,849	763,761
Deferred income taxes	410,166	326,290
Other liabilities	51,691	51,379
Total liabilities	1,658,392	1,539,940
Commitments and contingencies (Notes 7 and 16)
Stockholders' equity
Preferred stock, $0.01 par value, 50,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.01 par value, 150,000,000 shares authorized; 67,276,761 and 67,187,224 shares issued at September 30, 2013 and December 31, 2012, respectively	673	672
Common stock, held in treasury, at cost; 506,525 and 284,493 shares at September 30, 2013 and December 31, 2012, respectively	(32,711)	(13,302)
Additional paid-in capital	509,295	496,254
Retained earnings	1,798,721	1,399,472
Accumulated other comprehensive loss	(10,921)	(10,840)
Total stockholders' equity	2,265,057	1,872,256
Total liabilities and stockholders' equity	$ 3,923,449	$ 3,412,196