Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 98,500	$ 63,769
Restricted cash	2,532
Short-term investments	207,434	330,553
Accounts receivable	40,749	75,494
Allowance for doubtful accounts	(364)	(699)
Accounts receivable, net	40,385	74,795
Inventories:
Finished goods	26,329	28,893
Raw materials	1,799	1,990
Total inventories	28,128	30,883
Supplies, prepaid items and other:
Prepaid insurance	14,846	17,429
Precious metals	12,094	13,323
Supplies	30,486	27,501
Other	2,337	8,346
Total supplies, prepaid items and other	59,763	66,599
Total current assets	436,742	566,599
Property, plant and equipment, net	835,298	848,661
Other assets:
Operating lease assets	24,852	22,682
Intangible and other assets, net	1,292	1,877
Total other assets	26,144	24,559
Total assets	1,298,184	1,439,819
Current liabilities:
Accounts payable	68,323	78,182
Short-term financing	13,398	16,134
Accrued and other liabilities	30,961	38,470
Current portion of long-term debt	5,847	9,522
Total current liabilities	118,529	142,308
Long-term debt, net	575,874	702,733
Noncurrent operating lease liabilities	16,074	14,896
Other noncurrent accrued and other liabilities	523	522
Deferred income taxes	68,853	63,487
Commitments and contingencies (Note 7)
Stockholders' equity:
Common stock, $.10 par value; 150 million shares authorized, 91.2 million shares issued	9,117	9,117
Capital in excess of par value	501,026	497,179
Retained earnings	227,015	199,092
Total stockholders' equity	737,158	705,388
Less treasury stock, at cost:
Common stock, 18.1 million shares (14.9 million shares at December 31, 2022)	218,827	189,515
Total stockholders' equity	518,331	515,873
Total liabilities and stockholders' equity	$ 1,298,184	$ 1,439,819