Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 127,314	$ 186,811
Restricted cash and cash equivalents		365
Short-term investments		14,500
Accounts receivable, net	92,602	88,074
Inventories	53,237	56,586
Supplies, prepaid items and other:
Prepaid insurance	10,563	13,752
Precious metals	12,918	12,838
Supplies	18,681	15,927
Prepaid and refundable income taxes	6,811	7,387
Other	5,797	5,438
Total supplies, prepaid items and other	54,770	55,342
Deferred income taxes	4,774	17,204
Total current assets	332,697	418,882
Property, plant and equipment, net	1,005,488	619,205
Other assets:
Noncurrent restricted cash and cash equivalents		45,969
Noncurrent restricted investments		25,000
Intangible and other, net	23,642	21,516
Total other assets	23,642	92,485
Total assets	1,361,827	1,130,572
Current liabilities:
Accounts payable	108,002	81,456
Short-term financing	9,119	11,955
Accrued and other liabilities	52,331	51,166
Current portion of long-term debt	22,468	10,680
Total current liabilities	191,920	155,257
Long-term debt, net	497,954	440,205
Noncurrent accrued and other liabilities	20,922	17,934
Deferred income taxes	$ 52,179	$ 83,128
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $.10 par value; 75,000,000 shares authorized, 27,131,724 shares issued (26,968,212 shares at December 31, 2014)	$ 2,713	$ 2,697
Capital in excess of par value	192,249	170,537
Retained earnings	248,150	286,188
Stockholders equity including treasury stock	446,112	462,422
Less treasury stock, at cost:
Common stock, 3,735,503 shares (4,320,462 shares at December 31, 2014)	24,532	28,374
Total stockholders' equity	421,580	434,048
Total Liabilities and Stockholders' equity	1,361,827	1,130,572
Series E Preferred Stock [Member]
Redeemable preferred stocks:
Redeemable preferred stock, value	177,272
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