CONDENSED CONSOLIDATED BALANCE SHEET (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 158,147	$ 140,113
Restricted cash	10,767	11,578
Accounts receivable, net	182,700	214,724
Income taxes receivable	22,424	6,171
Inventories	17,395	15,270
Derivative instruments	0	26,209
Other current assets	4,633	1,650
Total current assets	396,066	415,715
Properties and equipment, net (Successful efforts method)	4,150,791	4,044,606
Other assets	63,710	63,211
TOTAL ASSETS	4,610,567	4,523,532
Current liabilities
Accounts payable	166,256	162,081
Current portion of long-term debt	100,000	188,000
Accrued liabilities	20,080	22,374
Interest payable	15,149	17,771
Derivative instruments	77,199	0
Total current liabilities	378,684	390,226
Long-term debt, net	946,316	945,924
Deferred income taxes	788,811	774,195
Asset retirement obligations	89,307	85,489
Postretirement benefits	31,633	30,713
Other liabilities	75,921	81,278
Total liabilities	2,310,672	2,307,825
Commitments and contingencies
Stockholders' equity
Common stock	47,862	47,783
Additional paid-in capital	1,815,770	1,804,354
Retained earnings	2,257,320	2,184,352
Accumulated other comprehensive income	2,144	2,419
Treasury stock	(1,823,201)	(1,823,201)
Total stockholders' equity	2,299,895	2,215,707
Total liabilities and stockholders' equity	$ 4,610,567	$ 4,523,532