Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 60,017	$ 127,195
Accounts receivable, net	51,299	49,601
Inventories	22,939	24,457
Supplies, prepaid items and other:
Prepaid insurance	11,217	10,563
Precious metals	8,648	12,918
Supplies	24,100	18,681
Prepaid and refundable income taxes	1,193	6,811
Other	1,733	4,701
Total supplies, prepaid items and other	46,891	53,674
Deferred income taxes		4,774
Current assets held for sale		72,996
Total current assets	181,146	332,697
Property, plant and equipment, net	1,078,958	978,709
Intangible and other assets, net	10,316	16,640
Noncurrent assets held for sale		33,781
Total assets	1,270,420	1,361,827
Current liabilities:
Accounts payable	54,246	87,999
Short-term financing	8,218	9,119
Accrued and other liabilities	44,037	39,808
Current portion of long-term debt	13,745	22,468
Current liabilities held for sale		32,526
Total current liabilities	120,246	191,920
Long-term debt, net	406,475	497,954
Noncurrent accrued and other liabilities	12,326	8,786
Noncurrent liabilities held for sale		12,136
Deferred income taxes	93,831	52,179
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $.10 par value; 75,000,000 shares authorized, 31,280,685 shares issued (27,131,724 shares at December 31, 2015)	3,128	2,713
Capital in excess of par value	192,172	192,249
Retained earnings	314,301	248,150
Stockholders equity including treasury stock	512,601	446,112
Less treasury stock, at cost:
Common stock, 3,004,855 shares (3,735,503 shares at December 31, 2015)	20,088	24,532
Total stockholders' equity	492,513	421,580
Total Liabilities and Stockholders' equity	1,270,420	1,361,827
Series E Preferred Stock [Member]
Redeemable preferred stocks:
Redeemable preferred stock, value	145,029	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