CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 216,413	$ 193,383
Short-term investments	8,504	14,675
Trade accounts receivable	81,417	99,471
Income tax receivable	0	12,925
Inventories, net	155,667	97,901
Prepaid expenses and other receivables	40,017	25,691
Total current assets	502,018	444,046
Mineral interests, net	102,879	110,130
Property, plant and equipment, net	607,406	606,200
Non-current income tax receivable	0	11,349
Deferred income taxes	163,565	154,297
Other long-term assets	15,145	18,242
Total assets	1,391,013	1,344,264
Current liabilities:
Accounts payable	50,002	46,436
Accrued expenses	67,515	65,755
Short term financing lease liabilities	11,874	10,146
Other current liabilities	9,886	6,615
Total current liabilities	139,277	128,952
Long-term debt	379,722	339,189
Asset retirement obligations	55,551	53,583
Long term financing lease liabilities	24,476	25,528
Other long-term liabilities	32,276	31,430
Total liabilities	631,302	578,682
Stockholders’ Equity:
Common stock, $0.01 par value per share (Authorized -140,000,000 shares as of September 30, 2020 and December 31, 2019, 53,408,040 issued and 51,186,199 outstanding as of September 30, 2020 and 53,293,449 issued and 51,071,608 outstanding as of December 31, 2019)	533	533
Preferred stock, $0.01 par value per share (10,000,000 shares authorized, no shares issued and outstanding)	0	0
Treasury stock, at cost (2,221,841 shares as of September 30, 2020 and December 31, 2019)	(50,576)	(50,576)
Additional paid in capital	247,907	243,932
Retained earnings	561,847	571,693
Total stockholders’ equity	759,711	765,582
Total liabilities and stockholders’ equity	$ 1,391,013	$ 1,344,264