CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 220,663	$ 193,383
Short-term investments	8,502	14,675
Trade accounts receivable	77,009	99,471
Income tax receivable	24,274	12,925
Inventories, net	153,905	97,901
Prepaid expenses and other receivables	34,967	25,691
Total current assets	519,320	444,046
Mineral interests, net	105,120	110,130
Property, plant and equipment, net	601,955	606,200
Non-current income tax receivable	0	11,349
Deferred income taxes	155,451	154,297
Other long-term assets	15,343	18,242
Total assets	1,397,189	1,344,264
Current liabilities:
Accounts payable	55,805	46,436
Accrued expenses	60,343	65,755
Short term financing lease liabilities	7,726	10,146
Other current liabilities	7,273	6,615
Total current liabilities	131,147	128,952
Long-term debt	379,541	339,189
Asset retirement obligations	54,986	53,583
Long term financing lease liabilities	24,731	25,528
Other long-term liabilities	31,821	31,430
Total liabilities	622,226	578,682
Stockholders’ Equity:
Common stock, $0.01 par value per share (Authorized -140,000,000 shares as of June 30, 2020 and December 31, 2019, 53,406,023 issued and 51,184,182 outstanding as of June 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, — shares issued and outstanding)	0	0
Treasury stock, at cost (2,221,841 shares as of June 30, 2020 and December 31, 2019)	(50,576)	(50,576)
Additional paid in capital	246,126	243,932
Retained earnings	578,880	571,693
Total stockholders’ equity	774,963	765,582
Total liabilities and stockholders’ equity	$ 1,397,189	$ 1,344,264