Discontinued Operations (Carrying Amounts of Assets and Liabilities Classified as Held for Sale on Consolidated Balance Sheets) (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Disposal Group Including Discontinued Operation Balance Sheet Disclosures [Abstract]
Cash and cash equivalents		$ 37	$ 31	$ 11
Accounts receivable		733	681
Other current assets		1,658	48
Midstream and other property and equipment, net	[1]	6,794	6,587
Goodwill	[1]	1,542	1,542
Other long-term assets	[1]		1,600
Total assets held for sale		10,764	10,489	$ 10,200
Accounts payable		213	186
Revenues and royalties payable		473	432
Other current liabilities		655	373
Long-term debt	[1]	3,590	3,542
Deferred income taxes	[1]	360	346
Other long-term liabilities	[1]		48
Total liabilities held for sale		$ 5,291	$ 4,927

[1] These amounts were reclassified to respective current assets and current liabilities held for sale as of June 30, 2018 with the sale of Devon’s interests in EnLink and the General Partner closing in July 2018