Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (200)	$ 773	$ 975
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depletion, depreciation and amortization	1,639	1,711	1,534
Impairment of oil and gas properties	0	0	77
Impairment of inventory and other property and equipment	3	38	11
Exploration expenses, including dry holes	11	8	27
Deferred income taxes	(52)	240	274
Gain (Loss) on Disposition of Property Plant Equipment	(9)	477	(290)
Gain (Loss) on Extinguishment of Debt	27	0	0
Accretion of discount on asset retirement obligations	9	10	14
Interest expense	51	9	5
Derivative related activity	325	(8)	(270)
Amortization of stock-based compensation	72	100	85
Investments in and Advances to Affiliate, Valuation Adjustment	64	(15)	0
South Texas contingent consideration valuation adjustment	42	45	0
South Texas deficiency fee obligation, net	80	0	0
Other	125	105	658
Change in operating assets and liabilities:
Accounts receivable	309	(227)	(52)
Inventories	(20)	(20)	(70)
Other assets	24	(33)	3
Accounts payable	(179)	(7)	321
Interest payable	(19)	0	(5)
Other liabilities	(219)	(91)	(55)
Net Cash Provided by (Used in) Operating Activities, Total	2,083	3,115	3,242
Cash flows from investing activities:
Proceeds from disposition of assets, net of cash sold	60	149	469
Proceeds from investments	0	624	1,373
Purchase of investments	(1)	0	(669)
Additions to oil and gas properties	(1,602)	(2,988)	(3,520)
Additions to other assets and other property and equipment, net	(125)	(232)	(263)
Net cash used in investing activities	(1,668)	(2,447)	(2,610)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net of discount	1,091	0	0
Proceeds from issuance of convertible senior notes	1,323	0	0
Purchase of derivatives related to issuance of convertible senior notes	(113)	0	0
Borrowing under credit facility	800	0	0
Repayment of credit facility	(800)	0	0
Repayment of senior notes, including tender offer premiums	(1,198)	0	(450)
Payments of other liabilities	(173)	(14)	(23)
Payments of financing fees	(36)	0	(4)
Purchases of treasury stock	(176)	(653)	(179)
Exercise of long-term incentive plan stock options and employee stock purchases	9	6	8
Dividends paid	(346)	(127)	(55)
Net cash provided by (used in) financing activities	381	(788)	(703)
Cash and Cash Equivalents, Period Increase (Decrease), Total	796	(120)	(71)
Cash, cash equivalents and restricted cash, beginning of period	705	825	896
Cash, cash equivalents and restricted cash, end of period	$ 1,501	$ 705	$ 825