CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 176,459	$ 143,750
Short-term investments	14,500
Accounts receivable, net	86,963	80,570
Inventories:
Finished goods	26,473	29,163
Work in progress	2,317	2,838
Raw materials	25,717	23,871
Total inventories	54,507	55,872
Supplies, prepaid items and other:
Prepaid insurance	7,094	15,073
Precious metals	12,867	14,927
Supplies	15,272	13,523
Prepaid income taxes	5,885	12,644
Other	3,823	3,867
Total supplies, prepaid items and other	44,941	60,034
Deferred income taxes	7,563	13,613
Total current assets	384,933	353,839
Property, plant and equipment, net	501,658	416,801
Other assets:
Noncurrent restricted cash and cash equivalents	148,096	80,974
Noncurrent restricted investments	50,000	209,990
Debt issuance costs, net	7,287	8,027
Other, net	16,948	13,466
Total other assets	222,331	312,457
Total assets	1,108,922	1,083,097
Current liabilities:
Accounts payable	72,128	61,775
Short-term financing	5,584	13,749
Accrued and other liabilities	42,519	49,107
Current portion of long-term debt	10,530	9,262
Total current liabilities	130,761	133,893
Long-term debt	449,798	453,705
Noncurrent accrued and other liabilities	17,463	17,086
Deferred income taxes	75,296	66,698
Commitments and contingencies (Note 9)
Stockholders' equity:
Common stock, $.10 par value; 75,000,000 shares authorized, 26,905,648 shares issued (26,846,470 at December 31, 2013)	2,691	2,685
Capital in excess of par value	168,979	167,550
Retained earnings	289,308	266,854
Stockholders equity including treasury stock	463,978	440,089
Less treasury stock, at cost:
Common stock, 4,320,462 shares	28,374	28,374
Total stockholders' equity	435,604	411,715
Total Liabilities and Stockholders' equity	1,108,922	1,083,097
Series B Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	2,000	2,000
Series D Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	$ 1,000	$ 1,000