CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Operating Activities
Net income (loss) including noncontrolling interest		$ 1,253,302,000	$ 419,486,000	[1],[2]	$ (311,789,000)	[1],[2]
Adjustments to reconcile net income (loss) to net cash provided by continuing operations activities:
(Income) loss from discontinued operations		(1,064,487,000)	(250,348,000)	[1],[2]	(241,226,000)	[1],[2]
Depreciation, depletion and amortization		1,147,842,000	775,614,000	[1],[2]	751,878,000	[1],[2]
Previously suspended exploration costs (credits)		12,840,000	20,508,000	[2]	(4,861,000)	[2]
Amortization of undeveloped leases		27,973,000	40,177,000	[2]	61,775,000	[2]
Accretion of asset retirement obligations		40,506,000	27,119,000	[1],[2]	25,282,000	[1],[2]
Impairment of assets		0	20,000,000	[1],[2]	0	[1],[2]
Deferred income tax charge (benefit)		28,530,000	(177,627,000)	[2]	270,072,000	[2]
Pretax (gain) loss from sale of assets		(227,000)	(54,000)	[2]	(127,434,000)	[2]
Mark to market loss (gain) on contingent consideration		8,672,000	(4,810,000)	[2]	0	[2]
Mark to market loss (gain) on crude contracts		33,364,000	(33,954,000)	[2]	(13,748,000)	[2]
Long-term non-cash compensation		76,958,000	72,151,000	[2]	44,119,000	[2]
Net (increase) decrease in noncash operating working capital		(16,887,000)	(16,103,000)	[2]	78,846,000	[2]
Other operating activities, net		(59,281,000)	(142,764,000)	[2]	80,437,000	[2]
Net cash provided by continuing operations activities		1,489,105,000	749,395,000	[2]	613,351,000	[2]
Investing Activities
Acquisition of oil and natural gas properties		(1,212,315,000)	(794,623,000)	[2]	0	[2]
Property additions and dry hole costs		(1,344,271,000)	(1,011,292,000)	[2]	(910,030,000)	[2]
Proceeds from sales of property, plant and equipment		20,382,000	1,175,000	[2]	69,506,000	[2]
Purchase of investment securities		0	0	[2]	(212,661,000)	[2]
Proceeds from maturity of investment securities		0	0	[2]	320,828,000	[2]
Net cash required by investing activities		(2,536,204,000)	(1,804,740,000)	[2]	(732,357,000)	[2]
Financing Activities
Borrowings on revolving credit facility and term loan		1,725,000,000	325,000,000	[2]	0	[2]
Repayment of revolving credit facility and term loan		(2,050,000,000)	0	[2]	0	[2]
Debt issuance, net of cost		542,394,000	0	[2]	541,597,000	[2]
Early retirement of debt		(521,332,000)	0	[2]	(550,000,000)	[2]
Loss on early extinguishment of debt		(26,626,000)	0	[2]	0	[2]
Repurchase of common stock		(499,924,000)	0	[2]	0	[2]
Capital lease obligation payments		(688,000)	(318,000)	[2]	0	[2]
Withholding tax on stock-based incentive awards		(6,991,000)	(8,076,000)	[2]	(7,116,000)	[2]
Distributions to noncontrolling interest		(128,158,000)	0	[2]	0	[2]
Cash dividends paid		(163,669,000)	(173,044,000)	[2]	(172,565,000)	[2]
Net cash (required) provided by financing activities		(1,129,994,000)	143,562,000	[2]	(188,084,000)	[2]
Cash Flows from Discontinued Operations
Operating activities	[3]	73,783,000	406,857,000	[2]	527,228,000	[2]
Investing activities	[3]	2,022,034,000	(91,398,000)	[2]	(99,637,000)	[2]
Financing activities	[3]	(4,914,000)	(9,432,000)	[2]	(17,133,000)	[2]
Net cash provided by discontinued operations	[3]	2,090,903,000	306,027,000	[2]	410,458,000	[2]
Cash transferred from discontinued operations to continuing operations		2,120,397,000	612,543,000	[2]	325,446,000	[2]
Effect of exchange rate changes on cash and cash equivalents		3,533,000	28,730,000	[2]	1,327,000	[2]
Net increase (decrease) in cash and cash equivalents		(53,163,000)	(270,510,000)	[2]	19,683,000	[2]
Cash and cash equivalents at beginning of period	[2]	359,923,000	630,433,000		610,750,000
Cash and cash equivalents at end of period		$ 306,760,000	$ 359,923,000	[2]	$ 630,433,000	[2]

[1] ¹ Reclassified to conform with current presentation (see Notes C and E). 2017 revenue is presented net of $58.9 million of transportation, gathering and processing costs as historically shown prior to the adoption of ASC 606 on January 1, 2018. See Notes to Consolidated Financial Statements, page 58.

[2] Reclassified to conform with current presentation (see Note E)

[3] Net cash provided by discontinued operations are not part of the cash flow reconciliation.