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Investments & NCI Sherwood Midstream Holdings (Details) - USD ($) $ in Millions			3 Months Ended	6 Months Ended
		Jan. 01, 2017	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Contribution of fixed assets to joint venture	[1]			$ 337	$ 0
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity			$ 1,100	1,100		$ 1,100
Distributions from unconsolidated affiliates - return of capital				24	$ 0
Equity method investments			3,368	$ 3,368		$ 2,471
Sherwood Midstream Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Fair Value Of Assets Contributed		$ 209	$ 10
Equity Method Investment, Ownership Percentage			86.00%	86.00%
Contribution of fixed assets to joint venture		203
Gain (Loss) on Disposition of Assets		2
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity			$ 14	$ 14
Distributions from unconsolidated affiliates - return of capital		$ 45
Equity method investments			$ 165	$ 165
Direct Ownership Interest [Member] | Sherwood Midstream Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage		79.00%
Indirect Ownership Interest [Member] | Sherwood Midstream Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage			13.90%	13.90%
Sherwood Midstream LLC [Member] | Sherwood Midstream Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage		21.00%
Payments to Acquire Interest in Joint Venture		$ 44	$ 4
[1] Contribution of assets to Sherwood Midstream and Sherwood Midstream Holdings. See Note 4.

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