CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Preferred stock, par value (usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (shares)	20,000,000	20,000,000
Preferred stock, shares outstanding (shares)	5,603,458	5,839,506
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	2,000,000,000	1,500,000,000
Common stock, shares issued	908,732,809	896,279,353
Treasury stock, common shares	2,240,394	1,220,504
VIE, cash and cash equivalents	$ 5	$ 882
VIE. proved oil and natural gas properties	68,858	66,451
VIE. accumulated depreciation, depletion and amortization	(63,664)	(62,726)
VIE. other current liabilities	1,455	1,798
Variable Interest Entities, Primary Beneficiary [Member]
VIE, cash and cash equivalents	2	1
VIE. proved oil and natural gas properties	488	488
VIE. accumulated depreciation, depletion and amortization	(461)	(458)
VIE. other current liabilities	$ 3	$ 3