Acquisitions And Divestitures (Narrative) (Details) $ in Millions, CAD in Billions			1 Months Ended		3 Months Ended			9 Months Ended
	Sep. 30, 2016 USD ($)	Jan. 07, 2016 USD ($) a	Oct. 31, 2016 USD ($)	Oct. 31, 2016 CAD	Sep. 30, 2016 USD ($) MMBoe	Jun. 30, 2016 USD ($) MMBoe	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Aug. 01, 2016
Business Acquisition [Line Items]
Divestitures of property and equipment					$ 1,680		$ 27	$ 1,889	$ 35
Gains on asset sales					1,351			$ 1,351
Access Pipeline [Member]
Business Acquisition [Line Items]
Ownership interest								50.00%
Access Pipeline [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment			$ 1,100	CAD 1.4
Gains on asset sales			$ 540
Divestiture agreement dedication initial term			25 years	25 years
Access Pipeline [Member] | Subsequent Event [Member] | Scenario Plan [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment			$ 120
Mississippian [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment						$ 200
Estimated proved reserves | MMBoe						11
Mississippian [Member] | US [Member] | Maximum [Member]
Business Acquisition [Line Items]
Percentage of Estimated proved reserves associated with divestiture assets						1.00%
East Texas, Anadarko Basin and Midland Basin [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment					$ 1,700
Estimated proved reserves | MMBoe					146
East Texas, Anadarko Basin and Midland Basin [Member] | US [Member]
Business Acquisition [Line Items]
Percentage of Estimated proved reserves associated with divestiture assets					9.00%
Oil and Gas Properties [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment					$ 1,653
Gains on asset sales					1,351
Installment Payable, Current [Member]
Business Acquisition [Line Items]
Installment payment	$ 243				243			$ 243
EnLink [Member]
Business Acquisition [Line Items]
Joint venture formation date								Aug. 01, 2016
Ownership interest percentage acquired										50.10%
Contribution of non monetary assets to joint venture								$ 244
Additional capital to fund potential future development projects								$ 262
Call rights to acquire increasing portions of joint venture partner's interest, start year								2021
Equity Issued in Business Combination [Member] | EnLink [Member]
Business Acquisition [Line Items]
Equity units value									$ 360
STACK [Member]
Business Acquisition [Line Items]
Close date of acquisition	Jan. 07, 2016
Number of net acres acquired | a		80,000
Aggregate purchase price		$ 1,500
Cash payment to acquire interest		849
Unproved properties	$ 1,300				1,300			$ 1,300
Proved properties	$ 200				200			200
STACK [Member] | Common Stock [Member] | Equity Issued in Business Combination [Member]
Business Acquisition [Line Items]
Equity units value		659
Anadarko Basin [Member] | EnLink [Member]
Business Acquisition [Line Items]
Close date of acquisition	Jan. 07, 2016
Aggregate purchase price		1,500
Cash payment to acquire interest		800
Amount committed to pay		$ 500
Commitment to pay cash due date		1 year
Installment payable, noncurrent	$ 250				250			250
Intangible assets	1,000				1,000			1,000
Property and equipment	400				400			400
Anadarko Basin [Member] | EnLink [Member] | Installment Payable, Noncurrent [Member]
Business Acquisition [Line Items]
Commitment to pay cash due date		24 months
Installment payable, noncurrent		$ 250
Anadarko Basin [Member] | EnLink [Member] | Installment Payable, Current [Member] | Undiscounted [Member]
Business Acquisition [Line Items]
Installment payment	$ 250				$ 250			250
Anadarko Basin [Member] | Common Stock [Member] | Equity Issued in Business Combination [Member] | General Partner [Member]
Business Acquisition [Line Items]
Equity units value		$ 215
Joint Venture Partner [Member] | EnLink [Member]
Business Acquisition [Line Items]
Ownership interest percentage acquired										49.90%
Additional capital to fund potential future development projects								400
Cash contribution								$ 138