Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 43,726	$ 32,433
Receivables:
Oil and natural gas sales	38,830	57,367
Joint interest, net	10,840	19,400
Income taxes	0	1,861
Total receivables	49,670	78,628
Prepaid expenses and other assets (Note 1)	13,832	30,691
Total current assets	107,228	141,752
Oil and natural gas properties and other, net – at cost: (Note 1)	686,878	748,798
Restricted deposits for asset retirement obligations	29,675	15,806
Deferred income taxes	94,331	63,916
Other assets (Note 1)	22,470	33,447
Total assets	940,582	1,003,719
Current liabilities:
Accounts payable	48,612	102,344
Undistributed oil and natural gas proceeds	19,167	29,450
Advances from joint interest partners	0	5,279
Asset retirement obligations	17,188	21,991
Accrued liabilities (Note 1)	29,880	30,896
Income tax payable	153	0
Total current liabilities	115,000	189,960
Long-term debt: (Note 2)
Principal	632,460	730,000
Carrying value adjustments	(7,174)	(10,467)
Long-term debt – carrying value	625,286	719,533
Asset retirement obligations, less current portion	375,516	333,603
Other liabilities (Note 1)	32,938	9,988
Deferred income taxes	128	0
Commitments and contingencies (Note 17)	0	0
Shareholders’ deficit:
Preferred stock, $0.00001 par value; 20,000 shares authorized; 0 issued at December 31, 2020 and December 31, 2019	0	0
Common stock, $0.00001 par value; 200,000 shares authorized; 145,174 issued and 142,305 outstanding at December 31, 2020 and 144,538 issued and 141,669 outstanding at December 31, 2019	1	1
Additional paid-in capital	550,339	547,050
Retained deficit	(734,459)	(772,249)
Treasury stock, at cost; 2,869 shares at December 31, 2020 and December 31, 2019	(24,167)	(24,167)
Total shareholders’ deficit	(208,286)	(249,365)
Total liabilities and shareholders’ deficit	$ 940,582	$ 1,003,719