Revenue Recognition Impact of Adoption of ASC 606 (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Service revenues	$ 1,346	$ 1,256
Service revenues - commodity consideration	101	0
Sales Revenue, Goods, Net	636	727
Total revenues	2,083	1,983
Cost of Purchased Oil and Gas	613	579
Processing commodity expenses	35	0
Operating Costs and Expenses	351	361
Depreciation and amortization expenses	423	433
Costs and Expenses	1,591	1,533
Operating Income (Loss)	492	450
Interest Costs Incurred	(218)	(221)
Interest capitalized	9	7
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	384	663
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	384	660
Net income (loss) attributable to noncontrolling interests	24	26
Net income (loss) attributable to controlling interests	360	634
Allocation of net income (loss) to common units	$ 353	$ 623
Basic earnings (loss) per common unit	$ 0.37	$ 0.68
Diluted earnings (loss) per common unit	$ 0.37	$ 0.68
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 386	$ 663
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	24	26
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	362	$ 637
Inventory, Net	160		$ 113
Other Assets, Current	198		176
Assets, Current	2,344		2,142
Property, Plant and Equipment, Gross	39,876		38,931
Property, Plant and Equipment, Net	28,547		27,912
Equity Method Investments	6,513		6,552
Intangible assets – net of accumulated amortization	8,643		8,790
Regulatory assets, deferred charges, and other	528		507
Total assets	46,575		45,903
Regulatory liabilities, deferred income, and other	3,221		2,809
Common and Class B units	21,694
Total partners’ equity	21,691		22,030
Noncontrolling interests in consolidated subsidiaries	1,654		1,659
Total equity	23,345		23,689
Total liabilities and equity	46,575		$ 45,903
Adoption of ASC 606	(148)
Net increase (decrease) in equity	(344)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Service revenues	5
Service revenues - commodity consideration	(101)
Sales Revenue, Goods, Net	10
Total revenues	(86)
Cost of Purchased Oil and Gas	(55)
Processing commodity expenses	(35)
Operating Costs and Expenses	(1)
Depreciation and amortization expenses	1
Costs and Expenses	(90)
Operating Income (Loss)	4
Interest Costs Incurred	3
Interest capitalized	(2)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	5
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	5
Net income (loss) attributable to noncontrolling interests	(1)
Net income (loss) attributable to controlling interests	6
Allocation of net income (loss) to common units	$ 6
Basic earnings (loss) per common unit	$ 0.01
Diluted earnings (loss) per common unit	$ 0.01
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 5
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	(1)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	6
Inventory, Net	(8)
Other Assets, Current	(20)
Assets, Current	(28)
Property, Plant and Equipment, Gross	(2)
Property, Plant and Equipment, Net	(2)
Equity Method Investments	(1)
Intangible assets – net of accumulated amortization	63
Regulatory assets, deferred charges, and other	(4)
Total assets	28
Regulatory liabilities, deferred income, and other	(125)
Common and Class B units	157
Total partners’ equity	157
Noncontrolling interests in consolidated subsidiaries	(4)
Total equity	153
Total liabilities and equity	28
Adoption of ASC 606	148
Net increase (decrease) in equity	153
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Service revenues	1,351
Service revenues - commodity consideration	0
Sales Revenue, Goods, Net	646
Total revenues	1,997
Cost of Purchased Oil and Gas	558
Processing commodity expenses	0
Operating Costs and Expenses	350
Depreciation and amortization expenses	424
Costs and Expenses	1,501
Operating Income (Loss)	496
Interest Costs Incurred	(215)
Interest capitalized	7
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	389
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	389
Net income (loss) attributable to noncontrolling interests	23
Net income (loss) attributable to controlling interests	366
Allocation of net income (loss) to common units	$ 359
Basic earnings (loss) per common unit	$ 0.38
Diluted earnings (loss) per common unit	$ 0.38
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 391
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	23
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	368
Inventory, Net	152
Other Assets, Current	178
Assets, Current	2,316
Property, Plant and Equipment, Gross	39,874
Property, Plant and Equipment, Net	28,545
Equity Method Investments	6,512
Intangible assets – net of accumulated amortization	8,706
Regulatory assets, deferred charges, and other	524
Total assets	46,603
Regulatory liabilities, deferred income, and other	3,096
Common and Class B units	21,851
Total partners’ equity	21,848
Noncontrolling interests in consolidated subsidiaries	1,650
Total equity	23,498
Total liabilities and equity	46,603
Adoption of ASC 606	0
Net increase (decrease) in equity	$ (191)