CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 130,155	$ 35,470
Short-term investments	17,501	17,501
Trade accounts receivable	113,750	117,746
Other receivables	11,354	14,482
Inventories, net	66,771	54,294
Prepaid expenses	28,020	29,376
Total current assets	367,551	268,869
Mineral interests, net	122,878	130,004
Property, plant and equipment, net	549,593	536,745
Income tax receivable	39,255	39,255
Other long-term assets	20,841	18,442
Total assets	1,100,118	993,315
Current liabilities:
Accounts payable	37,077	28,076
Accrued expenses	87,123	66,704
Other current liabilities	9,039	10,475
Current portion of long-term debt	1,512	2,965
Total current liabilities	134,751	108,220
Long-term debt	466,079	342,948
Asset retirement obligations	99,428	96,096
Other long-term liabilities	34,166	33,028
Total liabilities	734,424	580,292
Commitments and contingencies
Stockholders’ Equity:
Common stock, $0.01 par value per share (Authorized -140,000,000 shares, 53,256,428 issued and 52,756,440 outstanding as of September 30, 2018 and 53,256,440 issued and outstanding as of December 31, 2017)	534	534
Preferred stock, $0.01 par value per share (10,000,000 shares authorized, no shares issued and outstanding)	0	0
Treasury stock, at cost	(12,100)	0
Additional paid in capital	239,027	329,993
Retained earnings	138,233	82,496
Total stockholders’ equity	365,694	413,023
Total liabilities and stockholders’ equity	$ 1,100,118	$ 993,315