Investments in and Loans to Unconsolidated Affiliates - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity investments	$ 51			$ 48	$ 100	$ (117)
Goodwill, Impairment Loss					0
Distributions from equity investments					88	145
Distribution to equity investment					$ 148	0
DCP Midstream, LLC
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%				50.00%
Gulfstream Natural Gas System, LLC
Schedule of Equity Method Investments [Line Items]
Distributions from equity investments				396
Distribution to equity investment		$ 148	$ 248
Gain from limited partner units issuance | DCP Midstream, LLC
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity investments						2
Goodwill Impairment | DCP Midstream, LLC
Schedule of Equity Method Investments [Line Items]
Earnings (loss) from equity investments						(123)
DCP Midstream, LLC
Schedule of Equity Method Investments [Line Items]
Goodwill, Impairment Loss						460
Gulfstream Natural Gas System, LLC
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount				$ 800		$ 800