Organization And Summary Of Significant Accounting Policies (Narrative) (Details)			1 Months Ended				3 Months Ended	12 Months Ended			120 Months Ended	156 Months Ended
	Jan. 17, 2017 shares	Dec. 19, 2014 USD ($)	Sep. 30, 2016 USD ($)	Jul. 31, 2016 USD ($) $ / shares shares	Nov. 30, 2015	Jan. 31, 2015 USD ($) $ / shares shares	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) $ / shares $ / bbl $ / MMBTU shares	Dec. 31, 2015 USD ($) $ / shares $ / bbl $ / MMBTU shares	Dec. 31, 2014 USD ($) $ / bbl $ / MMBTU shares	Dec. 31, 2013 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)								$ 141,000,000	$ 201,000,000
Outstanding checks included in accounts payable								$ 8,000,000	$ 29,000,000			$ 8,000,000
Natural gas, oil and NGL reserves discount								10.00%	10.00%	10.00%
Period of time needed to calculate ceiling value of reserves								12 months	12 months	12 months
Net unevaluated costs excluded from amortization								$ 147,000,000	$ 332,000,000	$ 1,535,000,000	$ 91,000,000	$ 2,105,000,000
Impairment of natural gas and oil properties, net of tax			$ 506,000,000										$ 297,000,000	$ 641,000,000	$ 1,746,000,000	$ 944,000,000
Cash flow hedges impact on ceiling value, net of tax															$ 40,000,000	$ 60,000,000
Amount recognized is the largest amount of tax benefit, threshold								50.00%
Payments on long-term debt								$ 1,175,000,000	$ 500,000,000
Common stock, date dividend declared								Dec. 12, 2016
Common stock, shares issued as stock dividend | shares								7,166,389
Common stock, date dividend to be paid								Jan. 17, 2017
Antidilutive securities excluded from computation of earnings per share, shares | shares								83,287,879	76,856,343	1,475,883
Number of common shares: Effect of issuance of non-vested performance units | shares										273,918
Treasury stock, shares | shares								31,269	47,149			31,269
Unamortized debt expense								$ 28,000,000	$ 24,000,000			$ 28,000,000
Accounting Standards Update 2016-09 [Member] | Scenario, Forecast [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Unrecognized windfall tax benefits, cumulative-effect adjustment							$ 149,000,000
Long-term Debt [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Unamortized debt expense								28,000,000	24,000,000			28,000,000
Long-term Debt [Member] | Term Loan 1 due December 2020 [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Payments on long-term debt			48,000,000	$ 375,000,000
Debt instrument face amount								750,000,000				750,000,000
Debt instrument, term					3 years
Unamortized debt expense			$ 400,000					2,000,000	3,000,000			$ 2,000,000
Senior Notes [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Purchase of note principal				700,000,000
Proceeds from issuance of debt						$ 2,200,000,000		$ 2,200,000,000
Unamortized debt expense				$ 2,000,000
Bridge Loan [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Bridge loan		$ 4,500,000,000							$ 4,500,000,000	$ 4,500,000,000
Debt instrument, term		364 days							364 days	364 days
NGL [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairment of natural gas and oil properties, net of tax									$ 1,586,000,000
Full cost ceiling test, price | $ / bbl								6.74	6.82	23.79
United States [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Net unevaluated costs excluded from amortization								$ 2,105,000,000
Henry Hub Natural Gas [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Full cost ceiling test, price | $ / MMBTU								2.48	2.59	4.35
West Texas Intermediate Oil [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Full cost ceiling test, price | $ / bbl								39.25	46.79	91.48
Gathering Systems [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Straight-line depreciation period								25 years
Common Stock [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued | shares				98,900,000		30,000,000
Price per share | $ / shares				$ 13.00		$ 23.00
Proceeds from issuance of shares				$ 1,247,000,000		$ 669,000,000
Depositary Shares [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued | shares						34,500,000
Proceeds from issuance of shares						$ 1,700,000,000
Depositary shares conversion rate						0.05%
Liquidation preference per share | $ / shares						$ 50
Series B Preferred Stock [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Liquidation preference per share | $ / shares						$ 1,000		$ 1,000	$ 1,000			$ 1,000
Trading day period								20 days
Minimum [Member] | Depositary Shares [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued upon conversion | shares								1.85014				1.85014
Minimum [Member] | Series B Preferred Stock [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued upon conversion | shares								37.0028				37.0028
Potential number of shares issued upon conversion | shares								63,829,830
Maximum [Member] | Depositary Shares [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued upon conversion | shares								2.17391				2.17391
Maximum [Member] | Series B Preferred Stock [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares issued upon conversion | shares								43.4782				43.4782
Potential number of shares issued upon conversion | shares								74,999,895
WPX Property Acquisition [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Percentage of interest acquired									86.00%
Subsequent Event [Member]
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Common stock, shares issued as stock dividend | shares	2,751,410