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 (loss)	$ (56,672)	$ 2,023	$ (127,504)
Adjustments to net income (loss) to reconcile to net cash provided by operating activities:
Net change in fair value of unsettled commodity derivatives	145,246	(260,775)	17,260
Depreciation, depletion and amortization	644,152	559,793	469,084
Impairment of properties and equipment	38,536	458,397	285,887
Impairment of goodwill	0	0	75,121
Exploratory dry hole costs	0	113	41,297
Provision for uncollectible notes receivable	0	0	40,203
Loss on extinguishment of debt	0	0	24,747
Accretion of asset retirement obligations	6,117	5,075	6,306
Non-cash stock-based compensation	23,837	21,782	19,353
(Gain) loss on sale of properties and equipment	9,734	394	(766)
Amortization of debt discount and issuance costs	13,575	12,769	12,907
Deferred income taxes	(2,256)	6,105	(203,685)
Other	3,155	2,763	2,265
Total adjustments to net income (loss) to reconcile to net cash from operating activities:	882,096	806,416	709,573
Changes in current assets and liabilities:
Accounts receivable	(88,304)	12,025	(60,546)
Other assets	(11,560)	(81)	3,364
Production tax liability	22,240	35,225	31,316
Accounts payable and accrued expenses	(29,578)	16,261	31,378
Funds held for future distribution	(7,298)	9,973	24,472
Asset retirement obligations	(21,511)	(13,341)	(10,176)
Other liabilities	168,813	20,801	(4,064)
Total changes in assets and liabilities	32,802	80,863	15,744
Net cash from operating activities	858,226	889,302	597,813
Cash flows from investing activities:
Capital expenditures for development of crude oil and natural gas properties	(855,908)	(946,350)	(737,208)
Capital expenditures for other properties and equipment	(20,839)	(11,055)	(5,094)
Acquisition of crude oil and natural gas properties	(13,207)	(180,026)	(15,628)
Proceeds from sale of properties and equipment	2,105	3,562	9,991
Proceeds from divestitures	202,076	44,693	0
Sale of promissory note	0	0	40,203
Restricted cash	8,001	1,249	(9,250)
Sale of short-term investments	0	0	49,890
Purchase of short-term investments	0	0	(49,890)
Net cash from investing activities	(677,772)	(1,087,927)	(716,986)
Proceeds from revolving credit facility	1,577,000	1,072,500	0
Repayment of revolving credit facility	(1,605,500)	(1,040,000)	0
Proceeds from issuance of senior notes	0	0	592,366
Redemption of senior notes	0	0	(519,375)
Redemption of convertible notes			(519,375)
Payment of debt issuance costs	(72)	(7,704)	(50)
Purchase of treasury shares	(4,003)	(5,147)	(6,672)
Finance Lease, Principal Payments	(1,952)	(1,495)	(1,168)
Stock Repurchased and Retired During Period, Value	(154,363)	0	0
Other	0	(55)	(103)
Net cash from financing activities	(188,890)	18,099	64,998
Net change in cash, cash equivalents and restricted cash	(8,436)	(180,526)	(54,175)
Cash, cash equivalents and restricted cash, beginning of year	9,399	189,925	244,100
Cash, cash equivalents and restricted cash, end of year	$ 963	$ 9,399	$ 189,925