Acquisitions And Divestitures (Narrative) (Details) CAD in Millions, $ in Millions						1 Months Ended							3 Months Ended			12 Months Ended
		Jan. 07, 2016 USD ($) a	Dec. 17, 2015 USD ($) a	Mar. 07, 2014 USD ($)	Feb. 28, 2014 USD ($) a	Jan. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 31, 2016 USD ($)	Oct. 31, 2016 CAD	May 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Feb. 28, 2015 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($) MMBoe	Jun. 30, 2016 USD ($) MMBoe	Dec. 31, 2016 USD ($) MMBoe	Dec. 31, 2015 USD ($) MMBoe	Dec. 31, 2014 USD ($) MMBoe	Nov. 09, 2016	Aug. 01, 2016
Business Acquisition [Line Items]
Divestitures of property and equipment																$ 3,118	$ 107	$ 5,120
Estimated proved reserves associated with divestitures | MMBoe	[1]															157	7	383
Gains on asset sales													$ 540	$ 1,400		$ 1,893		$ 1,072
Foreign currency exchange loss																		(84)
Installment Payable, Current [Member]
Business Acquisition [Line Items]
Installment payment							$ 249						249			$ 249
Foreign Currency Derivatives [Member]
Business Acquisition [Line Items]
Loss on derivative																		$ 29
US [Member]
Business Acquisition [Line Items]
Estimated proved reserves associated with divestitures | MMBoe	[1]															157	7	207
Access Pipeline [Member]
Business Acquisition [Line Items]
Ownership interest																50.00%
Divestitures of property and equipment								$ 1,100	CAD 1,400
Gains on asset sales								$ 540
Divestiture agreement dedication initial term								25 years	25 years
Access Pipeline [Member] | Scenario Plan [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment | CAD									CAD 150
Access Pipeline [Member] | Maximum [Member]
Business Acquisition [Line Items]
Potential pipeline capacity committed, percentage								90.00%	90.00%
Mississippian [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment															$ 200
Estimated proved reserves associated with divestitures | 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 associated with divestitures | 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
Canadian Conventional and U.S Assets [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment																		$ 5,000
Canadian Conventional Assets [Member]
Business Acquisition [Line Items]
Gains on asset sales																		$ 1,100
Delaware Basin Joint Venture [Member] | EnLink [Member]
Business Acquisition [Line Items]
Joint venture formation date																Aug. 01, 2016
Ownership interest percentage acquired																				50.10%
Contribution of non monetary assets and cash to joint venture																$ 251
Future capital commitments																$ 285
Call rights to acquire increasing portions of joint venture partner's interest, start year																2021
Delaware Basin Joint Venture [Member] | EnLink [Member] | Joint Venture Partner [Member]
Business Acquisition [Line Items]
Ownership interest percentage acquired																				49.90%
Future capital commitments																$ 400
Cash contribution																$ 144
STACK [Member] | EnLink [Member]
Business Acquisition [Line Items]
Joint venture formation date																Nov. 09, 2016
Ownership interest percentage acquired																			30.00%
Future capital commitments																$ 40
Cash contribution																$ 29
STACK [Member] | EnLink [Member] | Joint Venture Partner [Member]
Business Acquisition [Line Items]
Ownership interest percentage acquired																			70.00%
Non-Core Midstream Assets [Member] | Scenario Plan [Member] | EnLink [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment							278
Victoria Express Pipeline [Member] | EnLink [Member]
Business Acquisition [Line Items]
Aggregate purchase price											$ 176
Estimated construction costs assumed											$ 35
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
Powder River Basin [Member]
Business Acquisition [Line Items]
Close date of acquisition																Dec. 17, 2015
Number of net acres acquired | a			253,000
Aggregate purchase price			$ 499
Cash payment to acquire interest			300
Unproved properties							393						393			$ 393
Proved properties							106						106			$ 106
Powder River Basin [Member] | Common Stock [Member] | Equity Issued in Business Combination [Member]
Business Acquisition [Line Items]
Equity units value			$ 199														$ 199
GeoSouthern Intermediate Holdings, LLC [Member]
Business Acquisition [Line Items]
Close date of acquisition																Feb. 28, 2014
Number of net acres acquired | a					82,000
Aggregate purchase price					$ 6,000
Unproved properties							1,000						1,000			$ 1,000
Proved properties							5,000						5,000			$ 5,000
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, plant and equipment							400						400			400
Anadarko Basin [Member] | Subsequent Event [Member] | EnLink [Member]
Business Acquisition [Line Items]
Installment payment, paid						$ 250
Anadarko Basin [Member] | Installment Payable, Noncurrent [Member] | EnLink [Member]
Business Acquisition [Line Items]
Commitment to pay cash due date		24 months
Installment payable, noncurrent		$ 250
Anadarko Basin [Member] | Installment Payable, Current [Member] | Undiscounted [Member] | EnLink [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
EnLink Midstream Holdings [Member] | EnLink [Member]
Business Acquisition [Line Items]
Equity units value										$ 900		$ 925
Ownership interest percentage acquired										25.00%		25.00%
General Partner And EnLink [Member]
Business Acquisition [Line Items]
Close date of acquisition																Mar. 07, 2014
Cash payment to acquire interest				$ 100
Intangible assets				569
Property, plant and equipment				$ 2,438

[1] Gas reserves are converted to Boe at the rate of six Mcf per Bbl of oil, based upon the approximate relative energy content of gas and oil. This rate is not necessarily indicative of the relationship of natural gas and oil prices. Bitumen and NGL reserves are converted to Boe on a one-to-one basis with oil.