CONDENSED CONSOLIDATED BALANCE SHEET (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 173,659	$ 140,113
Restricted cash	11,578	11,578
Accounts receivable, net	197,843	214,724
Income taxes receivable	2,559	6,171
Inventories	15,870	15,270
Derivative instruments	9,574	26,209
Other current assets	832	1,650
Total current assets	411,915	415,715
Properties and equipment, net (Successful efforts method)	4,075,428	4,044,606
Other assets	63,509	63,211
TOTAL ASSETS	4,550,852	4,523,532
Current liabilities
Accounts payable	169,101	162,081
Current portion of long-term debt	100,000	188,000
Accrued liabilities	21,240	22,374
Income taxes payable	19,895	0
Interest payable	4,856	17,771
Total current liabilities	315,092	390,226
Long-term debt, net	946,123	945,924
Deferred income taxes	786,526	774,195
Asset retirement obligations	87,410	85,489
Postretirement benefits	31,203	30,713
Other liabilities	78,528	81,278
Total liabilities	2,244,882	2,307,825
Commitments and contingencies
Stockholders' equity
Common stock	47,838	47,783
Additional paid-in capital	1,808,232	1,804,354
Retained earnings	2,270,819	2,184,352
Accumulated other comprehensive income	2,282	2,419
Treasury stock	(1,823,201)	(1,823,201)
Total stockholders' equity	2,305,970	2,215,707
Total liabilities and stockholders' equity	$ 4,550,852	$ 4,523,532