Investments in and Loans to Unconsolidated Affiliates -Summarized Financial Information, Income Statement (Details) - DCP Midstream, LLC - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 1,961	$ 1,851	$ 4,974	$ 5,763
Operating expenses	1,866	1,794	4,823	6,117
Operating income (loss)	95	57	151	(354)
Net income (loss)	94	25	126	(472)
Net income (loss) attributable to members’ interests	$ 26	$ (6)	$ 8	$ (509)