CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 42,283	$ 98,500
Restricted cash		2,532
Short-term investments	157,060	207,434
Accounts receivable	44,601	40,749
Allowance for doubtful accounts	(326)	(364)
Accounts receivable, net	44,275	40,385
Inventories:
Finished goods	19,259	26,329
Raw materials	2,127	1,799
Total inventories	21,386	28,128
Supplies, prepaid items and other:
Prepaid insurance	2,014	14,846
Precious metals	11,675	12,094
Supplies	31,421	30,486
Other	4,123	2,337
Total supplies, prepaid items and other	49,233	59,763
Total current assets	314,237	436,742
Property, plant and equipment, net	842,863	835,298
Other assets:
Operating lease assets	24,377	24,852
Intangible and other assets, net	1,456	1,292
Total other assets	25,833	26,144
Total assets	1,182,933	1,298,184
Current liabilities:
Accounts payable	75,734	68,323
Short-term financing	1,528	13,398
Accrued and other liabilities	36,107	30,961
Current portion of long-term debt	10,979	5,847
Total current liabilities	124,348	118,529
Long-term debt, net	475,991	575,874
Noncurrent operating lease liabilities	17,137	16,074
Other noncurrent accrued and other liabilities	523	523
Deferred income taxes	65,973	68,853
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	502,972	501,026
Retained earnings	216,811	227,015
Total stockholders' equity	728,900	737,158
Less treasury stock, at cost:
Common stock, 19.5 million shares (18.1 million shares at December 31, 2023)	229,939	218,827
Total stockholders' equity	498,961	518,331
Total liabilities and stockholders' equity	$ 1,182,933	$ 1,298,184