Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income	$ 216,959	$ 322,698	$ 163,152
Adjustments to reconcile net income to cash flows from operating activities
Depletion, depreciation, and amortization	233,816	216,449	207,713
Deferred income taxes	100,471	103,234	(95,779)
Stock-based compensation	12,470	11,951	15,154
Commodity derivatives expense (income)	70,078	(21,087)	77,576
Receipt (payment) on settlements of commodity derivatives	23,606	(175,248)	(47,795)
Gain on debt extinguishment	(155,998)	0	0
Debt issuance costs and discounts	12,303	6,246	6,191
Other, net	(8,596)	(4,725)	3,112
Changes in assets and liabilities, net of effects from acquisitions
Accrued production receivable	(13,619)	20,547	(21,398)
Trade and other receivables	9,379	16,094	(4,421)
Other current and long-term assets	7,629	(6,827)	(1,722)
Accounts payable and accrued liabilities	(3,275)	13,008	(24,710)
Oil and natural gas production payable	2,170	(15,300)	(3,997)
Other liabilities	(13,250)	42,645	(5,933)
Net cash provided by operating activities	494,143	529,685	267,143
Cash flows from investing activities
Oil and natural gas capital expenditures	(262,005)	(316,647)	(262,867)
Acquisitions of oil and natural gas properties	(79)	(541)	(88,886)
CO2 capital expenditures	(3,154)	(5,878)	(2,159)
Pipelines and plants capital expenditures	(27,319)	(23,108)	(2,540)
Net proceeds from sales of oil and natural gas properties and equipment	10,196	7,762	1,696
Other	12,669	5,136	(2,058)
Net cash used in investing activities	(269,692)	(333,276)	(356,814)
Cash flows from financing activities
Bank repayments	(925,791)	(1,982,653)	(1,589,000)
Bank borrowings	925,791	1,507,653	1,763,000
Interest payments treated as a reduction of debt	(85,303)	(79,606)	(50,349)
Proceeds from issuance of senior secured notes	0	450,000	0
Cash paid in conjunction with debt exchange	(136,427)	0	0
Repayment or repurchases of senior subordinated notes	0	0	(2,503)
Costs of debt financing	(11,065)	(16,060)	(6,289)
Pipeline financing and capital lease debt repayments	(13,908)	(23,300)	(27,462)
Other	348	(13,486)	1,216
Net cash provided by (used in) financing activities	(246,355)	(157,452)	88,613
Net increase (decrease) in cash, cash equivalents, and restricted cash	(21,904)	38,957	(1,058)
Cash, cash equivalents, and restricted cash at beginning of year	54,949	15,992	17,050
Cash, cash equivalents, and restricted cash at end of year	$ 33,045	$ 54,949	$ 15,992