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	Jan. 31, 2018 USD ($)	May 31, 2017 USD ($)	Jan. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 31, 2016 USD ($)	Oct. 31, 2016 CAD	May 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Feb. 28, 2015 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)		Nov. 09, 2016	Aug. 01, 2016
Business Acquisition [Line Items]
Divestitures of property and equipment															$ 417	$ 3,113	[1]	$ 107	[1]
Gain on asset dispositions															217	1,483	[1]	(7)	[1]
Asset retirement obligations assumed by purchasers															68	324
Installment payment, paid															250
Proceeds from sale of investment															190
EnLink [Member] | Howard Energy Partners [Member]
Business Acquisition [Line Items]
Proceeds from sale of investment												$ 190
Forecasted [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment				$ 1,000
Non Core Assets [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment															415
Gain on asset dispositions															$ 212
Asset retirement obligations assumed by purchasers																290
Goodwill allocated to divested assets						$ 80										80
Access Pipeline [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment							$ 1,100	CAD 1,400
Gain on asset dispositions							$ 540
Ownership interest							50.00%	50.00%
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%
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. 30, 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
US [Member] | Non Core Assets [Member]
Business Acquisition [Line Items]
Divestitures of property and equipment													$ 1,653	$ 200		1,853
Gain on asset dispositions													$ 726	$ 83		$ 809
Percentage of Estimated proved reserves associated with divestiture assets													9.00%	1.00%		10.00%
US [Member] | Non Core Assets [Member] | Maximum [Member]
Business Acquisition [Line Items]
Percentage of Estimated proved reserves associated with divestiture assets															1.00%
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
Proved properties															$ 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
Proved properties															$ 106
Powder River Basin [Member] | Common Stock [Member] | Equity Issued in Business Combination [Member]
Business Acquisition [Line Items]
Equity units value		$ 199
Anadarko Basin [Member] | EnLink [Member]
Business Acquisition [Line Items]
Close date of acquisition															Jan. 07, 2016
Aggregate purchase price	1,400
Cash payment to acquire interest	800
Intangible assets															$ 1,000
Property, plant and equipment															$ 400
Amount committed to pay	$ 500
Commitment to pay cash due date	1 year
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] | Subsequent Event [Member] | EnLink [Member]
Business Acquisition [Line Items]
Installment payment, paid			$ 250
Anadarko Basin [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%

[1] Prior year amounts have been recast due to change in accounting principle. See Note 2 in “Item 8. Financial Statements and Supplementary Data” of this report.