Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Income Tax [Line Items]
Valuation allowance against U.S. deferred tax assets, percent						100.00%	100.00%
U.S. statutory income tax rate						35.00%	35.00%		35.00%
Deferred income tax expense (benefit)						$ (294)	$ 41	[1]	$ (5,976)	[1]
Capital loss carryforward, deferred tax asset	$ 760					760	17
Goodwill, impairment loss							873
Allocated goodwill							83
Deferred tax assets, valuation allowance	968			$ 403		968	645		403
Net operating loss carryforwards, deferred tax assets	865					865	777
Unremitted foreign earnings	908					908
Unrecognized tax benefits, interest and penalties	28					28	68
Unrecognized tax benefit that would impact effective tax rate	115					115
Unrecognized tax benefits removed						101
Interest associated with tax examinations						50
United States Federal [Member]
Income Tax [Line Items]
Net operating loss carryforwards	2,400					2,400
Various U.S. States [Member]
Income Tax [Line Items]
Net operating loss carryforwards	1,700					$ 1,700
Minimum [Member] | United States Federal [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2036
Minimum [Member] | Canada Federal [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2029
Operating loss carryforward, utilization period						Dec. 31, 2018
Minimum [Member] | Various U.S. States [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2018
Maximum [Member] | United States Federal [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2037
Maximum [Member] | Canada Federal [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2037
Maximum [Member] | Various U.S. States [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2037
U.S. Oil And Gas Operations [Member]
Income Tax [Line Items]
Oil and Gas asset impairment charges									16,000
General Partner And EnLink [Member]
Income Tax [Line Items]
Goodwill, impairment loss			$ 873				873		$ 1,328
Goodwill and intangibles impairments				$ 1,600
General Partner And EnLink [Member] | United States Federal [Member]
Income Tax [Line Items]
Net operating loss carryforwards	259					$ 259
General Partner And EnLink [Member] | Various U.S. States [Member]
Income Tax [Line Items]
Net operating loss carryforwards	263					$ 263
General Partner And EnLink [Member] | Minimum [Member]
Income Tax [Line Items]
Operating loss carryforward, utilization period						Dec. 31, 2020
General Partner And EnLink [Member] | Minimum [Member] | United States Federal [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2034
General Partner And EnLink [Member] | Minimum [Member] | Various U.S. States [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2028
General Partner And EnLink [Member] | Maximum [Member] | United States Federal [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2037
General Partner And EnLink [Member] | Maximum [Member] | Various U.S. States [Member]
Income Tax [Line Items]
Operating loss carryforward, expiration date						Dec. 31, 2037
Forecasted [Member]
Income Tax [Line Items]
U.S. statutory income tax rate					21.00%
Change in Income Tax Rate [Member] | General Partner And EnLink [Member]
Income Tax [Line Items]
Deferred income tax expense (benefit)	211
Scenario Plan [Member]
Income Tax [Line Items]
Unrecognized tax benefits removed						$ 101
United States [Member]
Income Tax [Line Items]
Change in deferred tax valuation allowance						(323)	313
Allocated goodwill		$ 83
United States [Member] | Deferred Tax Assets [Member]
Income Tax [Line Items]
Change in deferred tax valuation allowance						(337)
United States [Member] | Transition Tax [Member]
Income Tax [Line Items]
Deferred income tax expense (benefit)	167
United States [Member] | Change in Income Tax Rate [Member]
Income Tax [Line Items]
Deferred income tax expense (benefit)	108
Canada [Member]
Income Tax [Line Items]
Change in deferred tax valuation allowance	641						$ 71
Capital loss carryforward, deferred tax asset	727					727
Deferred tax assets, valuation allowance	660					660
Net operating loss carryforwards	$ 710					$ 710

[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.