CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income		$ 103,528	$ 67,067	$ 168,186
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization		91,242	76,453	41,883
Deferred income tax benefit		(60,520)	0	0
Abandonment and impairment of unproved properties		37,343	11,201	5,271
Well abandonment costs and dry hole expense		(8)	172	0
Stock-based compensation		6,156	6,886	7,156
Non-cash lease component		(249)	668	0
Amortization of deferred financing costs		864	487	30
Derivative (gain) loss		(53,462)	37,145	(30,271)
Derivative cash settlements		49,406	1,691	(18,160)
(Gain) loss on property transactions, net		1,398	(1,177)	(27,324)
Other		71	3,559	(3,311)
Changes in current assets and liabilities:
Accounts receivable, net		24,945	(2,688)	(46,988)
Prepaid expenses and other assets		3,352	(2,415)	2,214
Accounts payable and accrued liabilities		(41,278)	28,320	19,953
Settlement of asset retirement obligations		(3,992)	(2,722)	(2,041)
Net cash provided by operating activities		158,796	224,647	116,598
Cash flows from investing activities:
Acquisition of oil and gas properties		(3,210)	(14,087)	(2,892)
Exploration and development of oil and gas properties		(60,149)	(242,487)	(264,231)
Proceeds from sale of oil and gas properties		0	1,757	103,134
Additions to property and equipment - non oil and gas		(440)	(341)	(387)
Net cash used in investing activities		(63,799)	(255,158)	(164,376)
Cash flows from financing activities:
Proceeds from credit facility		45,000	55,000	140,000
Payments to credit facility		(125,000)	(25,000)	(90,000)
Proceeds from exercise of stock options		0	0	1,100
Payment of employee tax withholdings in exchange for the return of common stock		(1,122)	(1,176)	(863)
Deferred financing costs		(23)	(220)	(2,239)
Principal payments on finance lease obligations		(102)	0	0
Net cash provided by (used in) financing activities		(81,247)	28,604	47,998
Net change in cash, cash equivalents, and restricted cash		13,750	(1,907)	220
Cash, cash equivalents, and restricted cash:
Beginning of period		11,095	13,002	12,782
End of period		24,845	11,095	13,002
Supplemental Cash Flow Disclosure:
Cash paid for interest, net of capitalization	[1]	1,546	4,110	2,582
Severance and ad valorem tax refund	[1]	0	352	0
Receivables exchanged for additional interests in oil and gas properties	[1]	8,299	0	0
Changes in working capital related to drilling expenditures	[1]	$ 2,795	$ 30,354	$ 11,769

[1] (1) Refer to Note 2 - Leases in the notes to the consolidated financial statements for discussion of right-of-use assets obtained in exchange for lease liabilities.