Consolidated Statements of Cash Flows (Audited) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Extinguishment of Debt, before Write off of Debt Issuance Cost	$ 24,747,000	$ 0	$ 0
Cash flows from operating activities:
Net loss	(127,504,000)	(245,928,000)	(68,280,000)
Adjustments to net income (loss) to reconcile to net cash provided by operating activities:
Net change in fair value of unsettled commodity derivatives	17,260,000	333,770,000	35,791,000
Depreciation, depletion and amortization	469,084,000	416,874,000	303,258,000
Provision for uncollectible notes receivable	(40,203,000)	44,038,000	0
Impairment of properties and equipment	285,887,000	9,973,000	161,620,000
Impairment of goodwill	75,121,000	0	0
Capitalized Exploratory Well Cost, Charged to Expense	41,297,000	0	0
Accretion of asset retirement obligations	6,306,000	7,080,000	6,293,000
Stock-based compensation	19,353,000	19,502,000	20,068,000
Gain on sale of properties and equipment	(766,000)	(43,000)	(385,000)
Amortization of debt discount and issuance costs	12,907,000	16,167,000	7,040,000
Deferred income taxes	(203,685,000)	(137,249,000)	(41,415,000)
Other	(2,265,000)	(2,603,000)	3,216,000
Total adjustments to net loss to reconcile to net cash from operating activities:	709,573,000	712,715,000	489,054,000
Changes in current assets and liabilities:
Accounts receivable	(60,546,000)	(32,627,000)	24,815,000
Other assets	(5,886,000)	2,303,000	(2,264,000)
Production tax liability	31,316,000	9,223,000	(1,629,000)
Accounts payable and accrued expenses	31,378,000	(162,000)	(30,310,000)
Funds held for distribution	24,472,000	36,510,000	2,699,000
Asset retirement obligations	(10,176,000)	(4,109,000)	(4,458,000)
Other liabilities	(4,064,000)	8,338,000	1,446,000
Total changes in assets and liabilities	6,494,000	19,476,000	(9,701,000)
Net cash from operating activities	588,563,000	486,263,000	411,073,000
Cash flows from investing activities:
Capital expenditures for development of crude oil and natural gas properties	(737,208,000)	(436,884,000)	(599,546,000)
Capital expenditures for other properties and equipment	(5,094,000)	(3,464,000)	(5,122,000)
Acquisition of crude oil and natural gas properties, including settlement adjustments and deposit for pending acquisition	(15,628,000)	(1,073,723,000)	0
Proceeds from sale of properties and equipment	9,991,000	4,945,000	405,000
Sale of promissory note	40,203,000	0	0
Increase (Decrease) in Restricted Cash	(9,250,000)	0	0
Sale of short-term investments	49,890,000	0	0
Purchase of short-term investments	(49,890,000)	0	0
Net cash from investing activities	(716,986,000)	(1,509,126,000)	(604,263,000)
Cash flows from financing activities:
Proceeds from issuance of equity, net of issuance costs	0	855,074,000	202,851,000
Proceeds from issuance of senior notes	592,366,000	392,172,000	0
Proceeds from issuance of convertible senior notes	0	193,935,000	0
Proceeds from revolving credit facility	0	85,000,000	397,000,000
Repayment of revolving credit facility	0	(122,000,000)	(416,000,000)
Redemption of senior notes	(519,375,000)	0	0
Redemption of convertible notes	0	(115,000,000)	0
Payment of debt issuance costs	(50,000)	(15,556,000)	(974,000)
Purchase of treasury shares	(6,672,000)	(6,935,000)	(6,055,000)
Other	(1,271,000)	(577,000)	1,152,000
Net cash from financing activities	64,998,000	1,266,113,000	177,974,000
Net change in cash and cash equivalents	(63,425,000)	243,250,000	(15,216,000)
Cash and cash equivalents, beginning of year	244,100,000	850,000	16,066,000
Cash and cash equivalents, end of year	$ 180,675,000	$ 244,100,000	$ 850,000