CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 48,949	$ 63,769
Short-term investments	376,882	330,553
Accounts receivable	60,251	75,494
Allowance for doubtful accounts	(693)	(699)
Accounts receivable, net	59,558	74,795
Inventories:
Finished goods	28,102	28,893
Raw materials	1,530	1,990
Total inventories	29,632	30,883
Supplies, prepaid items and other:
Prepaid insurance	12,271	17,429
Precious metals	14,474	13,323
Supplies	28,570	27,501
Other	9,491	8,346
Total supplies, prepaid items and other	64,806	66,599
Total current assets	579,827	566,599
Property, plant and equipment, net	842,925	848,661
Other assets:
Operating lease assets	21,321	22,682
Intangible and other assets, net	1,697	1,877
Total other assets	23,018	24,559
Total assets	1,445,770	1,439,819
Current liabilities:
Accounts payable	68,341	78,182
Short-term financing	10,168	16,134
Accrued and other liabilities	43,617	38,470
Current portion of long-term debt	8,544	9,522
Total current liabilities	130,670	142,308
Long-term debt, net	702,071	702,733
Noncurrent operating lease liabilities	13,460	14,896
Other noncurrent accrued and other liabilities	522	522
Deferred income taxes	69,095	63,487
Commitments and contingencies (Note 5)
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	497,216	497,179
Retained earnings	214,993	199,092
Stockholders equity including treasury stock	721,326	705,388
Less treasury stock, at cost:
Common stock, 15.0 million shares (14.9 million shares at December 31, 2022)	191,374	189,515
Total stockholders' equity	529,952	515,873
Total Liabilities and Stockholders' equity	$ 1,445,770	$ 1,439,819