CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 256,743	$ 193,383
Short-term investments	8,500	14,675
Trade accounts receivable	131,526	99,471
Income tax receivable	24,274	12,925
Inventories, net	117,563	97,901
Prepaid expenses and other receivables	25,925	25,691
Total current assets	564,531	444,046
Mineral interests, net	107,432	110,130
Property, plant and equipment, net	598,622	606,200
Non-current income tax receivable	0	11,349
Deferred income taxes	151,021	154,297
Other long-term assets	17,568	18,242
Total assets	1,439,174	1,344,264
Current liabilities:
Accounts payable	54,620	46,436
Accrued expenses	63,476	65,755
Short term financing lease liabilities	8,022	10,146
Other current liabilities	6,608	6,615
Current portion of long-term debt	0	0
Total current liabilities	132,726	128,952
Long-term debt	409,363	339,189
Asset retirement obligations	54,307	53,583
Long term financing lease liabilities	26,106	25,528
Other long-term liabilities	31,550	31,430
Total liabilities	654,052	578,682
Commitments and contingencies
Stockholders’ Equity:
Common stock, $0.01 par value per share (Authorized -140,000,000 shares as of March 31, 2020 and December 31, 2019, 53,387,591 issued and 51,165,750 outstanding as of March 31, 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 March 31, 2020 and December 31, 2019)	(50,576)	(50,576)
Additional paid in capital	244,525	243,932
Retained earnings	590,640	571,693
Total stockholders’ equity	785,122	765,582
Total liabilities and stockholders’ equity	$ 1,439,174	$ 1,344,264